### 4.9 Tabular data

#### 4.9.1 The `table` element

Categories:
  Flow content.
  Palpable content.
Contexts in which this element can be used:
  Where flow content is expected.
Content model:
  In this order: optionally a `caption` element, followed by zero or more `colgroup` elements, followed optionally by a `thead` element, followed optionally by a `tfoot` element, followed by either zero or more `tbody` elements or one or more `tr` elements, followed optionally by a `tfoot` element (but there can only be one `tfoot` element child in total), optionally intermixed with one or more script-supporting elements.
Tag omission in text/html:
  Neither tag is omissible.
Content attributes:
  Global attributes
  `sortable` — Enables a sorting interface for the table
DOM interface:

      interface HTMLTableElement : HTMLElement {
        attribute HTMLTableCaptionElement? caption;
        HTMLElement createCaption();
        void deleteCaption();
        attribute HTMLTableSectionElement? tHead;
        HTMLElement createTHead();
        void deleteTHead();
        attribute HTMLTableSectionElement? tFoot;
        HTMLElement createTFoot();
        void deleteTFoot();
        readonly attribute HTMLCollection tBodies;
        HTMLElement createTBody();
        readonly attribute HTMLCollection rows;
        HTMLElement insertRow(optional long index = -1);
        void deleteRow(long index);
        attribute boolean sortable;
        void stopSorting();
      };

The `table` element represents data with more than one dimension, in the form of a table.

The `table` element takes part in the table model. Tables have rows, columns, and cells given by their descendants. The rows and columns form a grid; a table's cells must completely cover that grid without overlap.

Precise rules for determining whether this conformance requirement is met are described in the description of the table model.

Authors are encouraged to provide information describing how to interpret complex tables. Guidance on how to provide such information is given below.

Tables must not be used as layout aids. Historically, some Web authors have misused tables in HTML as a way to control their page layout. This usage is non-conforming, because tools attempting to extract tabular data from such documents would obtain very confusing results. In particular, users of accessibility tools like screen readers are likely to find it very difficult to navigate pages with tables used for layout.

There are a variety of alternatives to using HTML tables for layout, primarily using CSS positioning and the CSS table model. [CSS]

Tables can be complicated to understand and navigate. To help users with this, user agents should clearly delineate cells in a table from each other, unless the user agent has classified the table as a (non-conforming) layout table.

Authors and implementors are encouraged to consider using some of the table design techniques described below to make tables easier to navigate for users.

User agents, especially those that do table analysis on arbitrary content, are encouraged to find heuristics to determine which tables actually contain data and which are merely being used for layout. This specification does not define a precise heuristic, but the following are suggested as possible indicators:

Feature | Indication
--- | ---
The use of the `role` attribute with the value `presentation` | Probably a layout table
The use of the non-conforming `border` attribute with the non-conforming value 0 | Probably a layout table
The use of the non-conforming `cellspacing` and `cellpadding` attributes with the value 0 | Probably a layout table
The use of `caption`, `thead`, or `th` elements | Probably a non-layout table
The use of the `headers` and `scope` attributes | Probably a non-layout table
The use of the non-conforming `border` attribute with a value other than 0 | Probably a non-layout table
Explicit visible borders set using CSS | Probably a non-layout table
The use of the `summary` attribute | Not a good indicator (both layout and non-layout tables have historically been given this attribute)

It is quite possible that the above suggestions are wrong. Implementors are urged to provide feedback elaborating on their experiences with trying to create a layout table detection heuristic.

If a `table` element has a (non-conforming) `summary` attribute, and the user agent has not classified the table as a layout table, the user agent may report the contents of that attribute to the user.

The `sortable` attribute is used in the table sorting model.

table . `caption` [ = value ]

  Returns the table's `caption` element.

  Can be set, to replace the `caption` element.

caption = table . `createCaption`()

  Ensures the table has a `caption` element, and returns it.

table . `deleteCaption`()

  Ensures the table does not have a `caption` element.

table . `tHead` [ = value ]

  Returns the table's `thead` element.

  Can be set, to replace the `thead` element. If the new value is not a `thead` element, throws a `HierarchyRequestError` exception.

thead = table . `createTHead`()

  Ensures the table has a `thead` element, and returns it.

table . `deleteTHead`()

  Ensures the table does not have a `thead` element.

table . `tFoot` [ = value ]

  Returns the table's `tfoot` element.

  Can be set, to replace the `tfoot` element. If the new value is not a `tfoot` element, throws a `HierarchyRequestError` exception.

tfoot = table . `createTFoot`()

  Ensures the table has a `tfoot` element, and returns it.

table . `deleteTFoot`()

  Ensures the table does not have a `tfoot` element.

table . `tBodies`

  Returns an `HTMLCollection` of the `tbody` elements of the table.

tbody = table . `createTBody`()

  Creates a `tbody` element, inserts it into the table, and returns it.

table . `rows`

  Returns an `HTMLCollection` of the `tr` elements of the table.

tr = table . `insertRow`( [ index ] )

  Creates a `tr` element, along with a `tbody` if required, inserts them into the table at the position given by the argument, and returns the `tr`.

  The position is relative to the rows in the table. The index −1, which is the default if the argument is omitted, is equivalent to inserting at the end of the table.

  If the given position is less than −1 or greater than the number of rows, throws an `IndexSizeError` exception.

table . `deleteRow`(index)

  Removes the `tr` element with the given position in the table.

  The position is relative to the rows in the table. The index −1 is equivalent to deleting the last row of the table.

  If the given position is less than −1 or greater than the index of the last row, or if there are no rows, throws an `IndexSizeError` exception.

The `caption` IDL attribute must return, on getting, the first `caption` element child of the `table` element, if any, or null otherwise. On setting, the first `caption` element child of the `table` element, if any, must be removed, and the new value, if not null, must be inserted as the first node of the `table` element.

The `createCaption()` method must return the first `caption` element child of the `table` element, if any; otherwise a new `caption` element must be created, inserted as the first node of the `table` element, and then returned.

The `deleteCaption()` method must remove the first `caption` element child of the `table` element, if any.

The `tHead` IDL attribute must return, on getting, the first `thead` element child of the `table` element, if any, or null otherwise. On setting, if the new value is null or a `thead` element, the first `thead` element child of the `table` element, if any, must be removed, and the new value, if not null, must be inserted immediately before the first element in the `table` element that is neither a `caption` element nor a `colgroup` element, if any, or at the end of the table if there are no such elements. If the new value is neither null nor a `thead` element, then a `HierarchyRequestError` DOM exception must be thrown instead.

The `createTHead()` method must return the first `thead` element child of the `table` element, if any; otherwise a new `thead` element must be created and inserted immediately before the first element in the `table` element that is neither a `caption` element nor a `colgroup` element, if any, or at the end of the table if there are no such elements, and then that new element must be returned.

The `deleteTHead()` method must remove the first `thead` element child of the `table` element, if any.

The `tFoot` IDL attribute must return, on getting, the first `tfoot` element child of the `table` element, if any, or null otherwise. On setting, if the new value is null or a `tfoot` element, the first `tfoot` element child of the `table` element, if any, must be removed, and the new value, if not null, must be inserted immediately before the first element in the `table` element that is neither a `caption` element, a `colgroup` element, nor a `thead` element, if any, or at the end of the table if there are no such elements. If the new value is neither null nor a `tfoot` element, then a `HierarchyRequestError` DOM exception must be thrown instead.

The `createTFoot()` method must return the first `tfoot` element child of the `table` element, if any; otherwise a new `tfoot` element must be created and inserted immediately before the first element in the `table` element that is neither a `caption` element, a `colgroup` element, nor a `thead` element, if any, or at the end of the table if there are no such elements, and then that new element must be returned.

The `deleteTFoot()` method must remove the first `tfoot` element child of the `table` element, if any.

The `tBodies` attribute must return an `HTMLCollection` rooted at the `table` node, whose filter matches only `tbody` elements that are children of the `table` element.

The `createTBody()` method must create a new `tbody` element, insert it immediately after the last `tbody` element child in the `table` element, if any, or at the end of the `table` element if the `table` element has no `tbody` element children, and then must return the new `tbody` element.

The `rows` attribute must return an `HTMLCollection` rooted at the `table` node, whose filter matches only `tr` elements that are either children of the `table` element, or children of `thead`, `tbody`, or `tfoot` elements that are themselves children of the `table` element. The elements in the collection must be ordered such that those elements whose parent is a `thead` are included first, in tree order, followed by those elements whose parent is either a `table` or `tbody` element, again in tree order, followed finally by those elements whose parent is a `tfoot` element, still in tree order.

The behaviour of the `insertRow(index)` method depends on the state of the table. When it is called, the method must act as required by the first item in the following list of conditions that describes the state of the table and the index argument:

If index is less than −1 or greater than the number of elements in `rows` collection:
  The method must throw an `IndexSizeError` exception.
If the `rows` collection has zero elements in it, and the `table` has no `tbody` elements in it:
  The method must create a `tbody` element, then create a `tr` element, then append the `tr` element to the `tbody` element, then append the `tbody` element to the `table` element, and finally return the `tr` element.
If the `rows` collection has zero elements in it:
  The method must create a `tr` element, append it to the last `tbody` element in the table, and return the `tr` element.
If index is −1 or equal to the number of items in `rows` collection:
  The method must create a `tr` element, and append it to the parent of the last `tr` element in the `rows` collection. Then, the newly created `tr` element must be returned.
Otherwise:
  The method must create a `tr` element, insert it immediately before the indexth `tr` element in the `rows` collection, in the same parent, and finally must return the newly created `tr` element.

When the `deleteRow(index)` method is called, the user agent must run the following steps:

1. If index is equal to −1, then index must be set to the number of items in the `rows` collection, minus one.

2. Now, if index is less than zero, or greater than or equal to the number of elements in the `rows` collection, the method must instead throw an `IndexSizeError` exception, and these steps must be aborted.

3. Otherwise, the method must remove the indexth element in the `rows` collection from its parent.

The `stopSorting()` method is used in the table sorting model.

The IDL attribute `sortable` must reflect the `sortable` content attribute.

Here is an example of a table being used to mark up a Sudoku puzzle. Observe the lack of headers, which are not necessary in such a table.

    <section>
     <style scoped>
      table { border-collapse: collapse; border: solid thick; }
      colgroup, tbody { border: solid medium; }
      td { border: solid thin; height: 1.4em; width: 1.4em; text-align: center; padding: 0; }
     </style>
     <h1>Today's Sudoku</h1>
     <table>
      <colgroup><col><col><col>
      <colgroup><col><col><col>
      <colgroup><col><col><col>
      <tbody>
       <tr> <td> 1 <td>   <td> 3 <td> 6 <td>   <td> 4 <td> 7 <td>   <td> 9
       <tr> <td>   <td> 2 <td>   <td>   <td> 9 <td>   <td>   <td> 1 <td>
       <tr> <td> 7 <td>   <td>   <td>   <td>   <td>   <td>   <td>   <td> 6
      <tbody>
       <tr> <td> 2 <td>   <td> 4 <td>   <td> 3 <td>   <td> 9 <td>   <td> 8
       <tr> <td>   <td>   <td>   <td>   <td>   <td>   <td>   <td>   <td>
       <tr> <td> 5 <td>   <td>   <td> 9 <td>   <td> 7 <td>   <td>   <td> 1
      <tbody>
       <tr> <td> 6 <td>   <td>   <td>   <td> 5 <td>   <td>   <td>   <td> 2
       <tr> <td>   <td>   <td>   <td>   <td> 7 <td>   <td>   <td>   <td>
       <tr> <td> 9 <td>   <td>   <td> 8 <td>   <td> 2 <td>   <td>   <td> 5
     </table>
    </section>

##### 4.9.1.1 Techniques for describing tables

For tables that consist of more than just a grid of cells with headers in the first row and headers in the first column, and for any table in general where the reader might have difficulty understanding the content, authors should include explanatory information introducing the table. This information is useful for all users, but is especially useful for users who cannot see the table, e.g. users of screen readers.

Such explanatory information should introduce the purpose of the table, outline its basic cell structure, highlight any trends or patterns, and generally teach the user how to use the table.

For instance, the following table:

Characteristics with positive and negative sides
Negative | Characteristic | Positive
--- | --- | ---
Sad | Mood | Happy
Failing | Grade | Passing

...might benefit from a description explaining the way the table is laid out, something like "Characteristics are given in the second column, with the negative side in the left column and the positive side in the right column".

There are a variety of ways to include this information, such as:

In prose, surrounding the table

      <p>In the following table, characteristics are given in the second
      column, with the negative side in the left column and the positive
      side in the right column.</p>
      <table>
       <caption>Characteristics with positive and negative sides</caption>
       <thead>
        <tr>
         <th id="n"> Negative
         <th> Characteristic
         <th> Positive
       <tbody>
        <tr>
         <td headers="n r1"> Sad
         <th id="r1"> Mood
         <td> Happy
        <tr>
         <td headers="n r2"> Failing
         <th id="r2"> Grade
         <td> Passing
      </table>

In the table's `caption`

      <table>
       <caption>
        <strong>Characteristics with positive and negative sides.</strong>
        <p>Characteristics are given in the second column, with the
        negative side in the left column and the positive side in the right
        column.</p>
       </caption>
       <thead>
        <tr>
         <th id="n"> Negative
         <th> Characteristic
         <th> Positive
       <tbody>
        <tr>
         <td headers="n r1"> Sad
         <th id="r1"> Mood
         <td> Happy
        <tr>
         <td headers="n r2"> Failing
         <th id="r2"> Grade
         <td> Passing
      </table>

In the table's `caption`, in a `details` element

      <table>
       <caption>
        <strong>Characteristics with positive and negative sides.</strong>
        <details>
         <summary>Help</summary>
         <p>Characteristics are given in the second column, with the
         negative side in the left column and the positive side in the right
         column.</p>
        </details>
       </caption>
       <thead>
        <tr>
         <th id="n"> Negative
         <th> Characteristic
         <th> Positive
       <tbody>
        <tr>
         <td headers="n r1"> Sad
         <th id="r1"> Mood
         <td> Happy
        <tr>
         <td headers="n r2"> Failing
         <th id="r2"> Grade
         <td> Passing
      </table>

Next to the table, in the same `figure`

      <figure>
       <figcaption>Characteristics with positive and negative sides</figcaption>
       <p>Characteristics are given in the second column, with the
       negative side in the left column and the positive side in the right
       column.</p>
       <table>
        <thead>
         <tr>
          <th id="n"> Negative
          <th> Characteristic
          <th> Positive
        <tbody>
         <tr>
          <td headers="n r1"> Sad
          <th id="r1"> Mood
          <td> Happy
         <tr>
          <td headers="n r2"> Failing
          <th id="r2"> Grade
          <td> Passing
       </table>
      </figure>

Next to the table, in a `figure`'s `figcaption`

      <figure>
       <figcaption>
        <strong>Characteristics with positive and negative sides</strong>
        <p>Characteristics are given in the second column, with the
        negative side in the left column and the positive side in the right
        column.</p>
       </figcaption>
       <table>
        <thead>
         <tr>
          <th id="n"> Negative
          <th> Characteristic
          <th> Positive
        <tbody>
         <tr>
          <td headers="n r1"> Sad
          <th id="r1"> Mood
          <td> Happy
         <tr>
          <td headers="n r2"> Failing
          <th id="r2"> Grade
          <td> Passing
       </table>
      </figure>

Authors may also use other techniques, or combinations of the above techniques, as appropriate.

The best option, of course, rather than writing a description explaining the way the table is laid out, is to adjust the table such that no explanation is needed.

In the case of the table used in the examples above, a simple rearrangement of the table so that the headers are on the top and left sides removes the need for an explanation as well as removing the need for the use of `headers` attributes:

    <table>
     <caption>Characteristics with positive and negative sides</caption>
     <thead>
      <tr>
       <th> Characteristic
       <th> Negative
       <th> Positive
     <tbody>
      <tr>
       <th> Mood
       <td> Sad
       <td> Happy
      <tr>
       <th> Grade
       <td> Failing
       <td> Passing
    </table>

##### 4.9.1.2 Techniques for table design

Good table design is key to making tables more readable and usable.

In visual media, providing column and row borders and alternating row backgrounds can be very effective to make complicated tables more readable.

For tables with large volumes of numeric content, using monospaced fonts can help users see patterns, especially in situations where a user agent does not render the borders. (Unfortunately, for historical reasons, not rendering borders on tables is a common default.)

In speech media, table cells can be distinguished by reporting the corresponding headers before reading the cell's contents, and by allowing users to navigate the table in a grid fashion, rather than serialising the entire contents of the table in source order.

Authors are encouraged to use CSS to achieve these effects.

User agents are encouraged to render tables using these techniques whenever the page does not use CSS and the table is not classified as a layout table.

#### 4.9.2 The `caption` element

Categories:
  None.
Contexts in which this element can be used:
  As the first element child of a `table` element.
Content model:
  Flow content, but with no descendant `table` elements.
Tag omission in text/html:
  A `caption` element's end tag can be omitted if the `caption` element is not immediately followed by a space character or a comment.
Content attributes:
  Global attributes
DOM interface:

      interface HTMLTableCaptionElement : HTMLElement {};

The `caption` element represents the title of the `table` that is its parent, if it has a parent and that is a `table` element.

The `caption` element takes part in the table model.

When a `table` element is the only content in a `figure` element other than the `figcaption`, the `caption` element should be omitted in favor of the `figcaption`.

A caption can introduce context for a table, making it significantly easier to understand.

Consider, for instance, the following table:

| 1 | 2 | 3 | 4 | 5 | 6
--- | --- | --- | --- | --- | --- | ---
1 | 2 | 3 | 4 | 5 | 6 | 7
2 | 3 | 4 | 5 | 6 | 7 | 8
3 | 4 | 5 | 6 | 7 | 8 | 9
4 | 5 | 6 | 7 | 8 | 9 | 10
5 | 6 | 7 | 8 | 9 | 10 | 11
6 | 7 | 8 | 9 | 10 | 11 | 12

In the abstract, this table is not clear. However, with a caption giving the table's number (for reference in the main prose) and explaining its use, it makes more sense:

    <caption>
    <p>Table 1.
    <p>This table shows the total score obtained from rolling two
    six-sided dice. The first row represents the value of the first die,
    the first column the value of the second die. The total is given in
    the cell that corresponds to the values of the two dice.
    </caption>

This provides the user with more context:

Table 1.

This table shows the total score obtained from rolling two six-sided dice. The first row represents the value of the first die, the first column the value of the second die. The total is given in the cell that corresponds to the values of the two dice.

| 1 | 2 | 3 | 4 | 5 | 6
--- | --- | --- | --- | --- | --- | ---
1 | 2 | 3 | 4 | 5 | 6 | 7
2 | 3 | 4 | 5 | 6 | 7 | 8
3 | 4 | 5 | 6 | 7 | 8 | 9
4 | 5 | 6 | 7 | 8 | 9 | 10
5 | 6 | 7 | 8 | 9 | 10 | 11
6 | 7 | 8 | 9 | 10 | 11 | 12

#### 4.9.3 The `colgroup` element

Categories:
  None.
Contexts in which this element can be used:
  As a child of a `table` element, after any `caption` elements and before any `thead`, `tbody`, `tfoot`, and `tr` elements.
Content model:
  If the `span` attribute is present: Nothing.
  If the `span` attribute is absent: Zero or more `col` and `template` elements.
Tag omission in text/html:
  A `colgroup` element's start tag can be omitted if the first thing inside the `colgroup` element is a `col` element, and if the element is not immediately preceded by another `colgroup` element whose end tag has been omitted. (It can't be omitted if the element is empty.)
  A `colgroup` element's end tag can be omitted if the `colgroup` element is not immediately followed by a space character or a comment.
Content attributes:
  Global attributes
  `span` — Number of columns spanned by the element
DOM interface:

      interface HTMLTableColElement : HTMLElement {
        attribute unsigned long span;
      };

The `colgroup` element represents a group of one or more columns in the `table` that is its parent, if it has a parent and that is a `table` element.

If the `colgroup` element contains no `col` elements, then the element may have a `span` content attribute specified, whose value must be a valid non-negative integer greater than zero.

The `colgroup` element and its `span` attribute take part in the table model.

The `span` IDL attribute must reflect the content attribute of the same name. The value must be limited to only non-negative numbers greater than zero.

#### 4.9.4 The `col` element

Categories:
  None.
Contexts in which this element can be used:
  As a child of a `colgroup` element that doesn't have a `span` attribute.
Content model:
  Nothing.
Tag omission in text/html:
  No end tag.
Content attributes:
  Global attributes
  `span` — Number of columns spanned by the element
DOM interface:

  `HTMLTableColElement`, same as for `colgroup` elements. This interface defines one member, `span`.

If a `col` element has a parent and that is a `colgroup` element that itself has a parent that is a `table` element, then the `col` element represents one or more columns in the column group represented by that `colgroup`.

The element may have a `span` content attribute specified, whose value must be a valid non-negative integer greater than zero.

The `col` element and its `span` attribute take part in the table model.

The `span` IDL attribute must reflect the content attribute of the same name. The value must be limited to only non-negative numbers greater than zero.

#### 4.9.5 The `tbody` element

Categories:
  None.
Contexts in which this element can be used:
  As a child of a `table` element, after any `caption`, `colgroup`, and `thead` elements, but only if there are no `tr` elements that are children of the `table` element.
Content model:
  Zero or more `tr` and script-supporting elements
Tag omission in text/html:
  A `tbody` element's start tag can be omitted if the first thing inside the `tbody` element is a `tr` element, and if the element is not immediately preceded by a `tbody`, `thead`, or `tfoot` element whose end tag has been omitted. (It can't be omitted if the element is empty.)
  A `tbody` element's end tag can be omitted if the `tbody` element is immediately followed by a `tbody` or `tfoot` element, or if there is no more content in the parent element.
Content attributes:
  Global attributes
DOM interface:

      interface HTMLTableSectionElement : HTMLElement {
        readonly attribute HTMLCollection rows;
        HTMLElement insertRow(optional long index = -1);
        void deleteRow(long index);
      };

  The `HTMLTableSectionElement` interface is also used for `thead` and `tfoot` elements.

The `tbody` element represents a block of rows that consist of a body of data for the parent `table` element, if the `tbody` element has a parent and it is a `table`.

The `tbody` element takes part in the table model.

tbody . `rows`

  Returns an `HTMLCollection` of the `tr` elements of the table section.

tr = tbody . `insertRow`( [ index ] )

  Creates a `tr` element, inserts it into the table section at the position given by the argument, and returns the `tr`.

  The position is relative to the rows in the table section. The index −1, which is the default if the argument is omitted, is equivalent to inserting at the end of the table section.

  If the given position is less than −1 or greater than the number of rows, throws an `IndexSizeError` exception.

tbody . `deleteRow`(index)

  Removes the `tr` element with the given position in the table section.

  The position is relative to the rows in the table section. The index −1 is equivalent to deleting the last row of the table section.

  If the given position is less than −1 or greater than the index of the last row, or if there are no rows, throws an `IndexSizeError` exception.

The `rows` attribute must return an `HTMLCollection` rooted at the element, whose filter matches only `tr` elements that are children of the element.

The `insertRow(index)` method must, when invoked on an element table section, act as follows:

If index is less than −1 or greater than the number of elements in the `rows` collection, the method must throw an `IndexSizeError` exception.

If index is −1 or equal to the number of items in the `rows` collection, the method must create a `tr` element, append it to the element table section, and return the newly created `tr` element.

Otherwise, the method must create a `tr` element, insert it as a child of the table section element, immediately before the indexth `tr` element in the `rows` collection, and finally must return the newly created `tr` element.

The `deleteRow(index)` method must remove the indexth element in the `rows` collection from its parent. If index is less than zero or greater than or equal to the number of elements in the `rows` collection, the method must instead throw an `IndexSizeError` exception.

#### 4.9.6 The `thead` element

Categories:
  None.
Contexts in which this element can be used:
  As a child of a `table` element, after any `caption`, and `colgroup` elements and before any `tbody`, `tfoot`, and `tr` elements, but only if there are no other `thead` elements that are children of the `table` element.
Content model:
  Zero or more `tr` and script-supporting elements
Tag omission in text/html:
  A `thead` element's end tag can be omitted if the `thead` element is immediately followed by a `tbody` or `tfoot` element.
Content attributes:
  Global attributes
DOM interface:
  `HTMLTableSectionElement`, as defined for `tbody` elements.

The `thead` element represents the block of rows that consist of the column labels (headers) for the parent `table` element, if the `thead` element has a parent and it is a `table`.

The `thead` element takes part in the table model.

This example shows a `thead` element being used. Notice the use of both `th` and `td` elements in the `thead` element: the first row is the headers, and the second row is an explanation of how to fill in the table.

    <table>
     <caption> School auction sign-up sheet </caption>
     <thead>
      <tr>
       <th><label for=e1>Name</label>
       <th><label for=e2>Product</label>
       <th><label for=e3>Picture</label>
       <th><label for=e4>Price</label>
      <tr>
       <td>Your name here
       <td>What are you selling?
       <td>Link to a picture
       <td>Your reserve price
     <tbody>
      <tr>
       <td>Ms Danus
       <td>Doughnuts
       <td><img src="http://example.com/mydoughnuts.png" title="Doughnuts from Ms Danus">
       <td>$45
      <tr>
       <td><input id=e1 type=text name=who required form=f>
       <td><input id=e2 type=text name=what required form=f>
       <td><input id=e3 type=url name=pic form=f>
       <td><input id=e4 type=number step=0.01 min=0 value=0 required form=f>
    </table>
    <form id=f action="/auction.cgi">
     <input type=button name=add value="Submit">
    </form>

#### 4.9.7 The `tfoot` element

Categories:
  None.
Contexts in which this element can be used:
  As a child of a `table` element, after any `caption`, `colgroup`, and `thead` elements and before any `tbody` and `tr` elements, but only if there are no other `tfoot` elements that are children of the `table` element.
  As a child of a `table` element, after any `caption`, `colgroup`, `thead`, `tbody`, and `tr` elements, but only if there are no other `tfoot` elements that are children of the `table` element.
Content model:
  Zero or more `tr` and script-supporting elements
Tag omission in text/html:
  A `tfoot` element's end tag can be omitted if the `tfoot` element is immediately followed by a `tbody` element, or if there is no more content in the parent element.
Content attributes:
  Global attributes
DOM interface:
  `HTMLTableSectionElement`, as defined for `tbody` elements.

The `tfoot` element represents the block of rows that consist of the column summaries (footers) for the parent `table` element, if the `tfoot` element has a parent and it is a `table`.

The `tfoot` element takes part in the table model.

#### 4.9.8 The `tr` element

Categories:
  None.
Contexts in which this element can be used:
  As a child of a `thead` element.
  As a child of a `tbody` element.
  As a child of a `tfoot` element.
  As a child of a `table` element, after any `caption`, `colgroup`, and `thead` elements, but only if there are no `tbody` elements that are children of the `table` element.
Content model:
  Zero or more `td`, `th`, and script-supporting elements
Tag omission in text/html:
  A `tr` element's end tag can be omitted if the `tr` element is immediately followed by another `tr` element, or if there is no more content in the parent element.
Content attributes:
  Global attributes
DOM interface:

      interface HTMLTableRowElement : HTMLElement {
        readonly attribute long rowIndex;
        readonly attribute long sectionRowIndex;
        readonly attribute HTMLCollection cells;
        HTMLElement insertCell(optional long index = -1);
        void deleteCell(long index);
      };

The `tr` element represents a row of cells in a table.

The `tr` element takes part in the table model.

tr . `rowIndex`

  Returns the position of the row in the table's `rows` list.

  Returns −1 if the element isn't in a table.

tr . `sectionRowIndex`

  Returns the position of the row in the table section's `rows` list.

  Returns −1 if the element isn't in a table section.

tr . `cells`

  Returns an `HTMLCollection` of the `td` and `th` elements of the row.

cell = tr . `insertCell`( [ index ] )

  Creates a `td` element, inserts it into the table row at the position given by the argument, and returns the `td`.

  The position is relative to the cells in the row. The index −1, which is the default if the argument is omitted, is equivalent to inserting at the end of the row.

  If the given position is less than −1 or greater than the number of cells, throws an `IndexSizeError` exception.

tr . `deleteCell`(index)

  Removes the `td` or `th` element with the given position in the row.

  The position is relative to the cells in the row. The index −1 is equivalent to deleting the last cell of the row.

  If the given position is less than −1 or greater than the index of the last cell, or if there are no cells, throws an `IndexSizeError` exception.

The `rowIndex` attribute must, if the element has a parent `table` element, or a parent `tbody`, `thead`, or `tfoot` element and a grandparent `table` element, return the index of the `tr` element in that `table` element's `rows` collection. If there is no such `table` element, then the attribute must return −1.

The `sectionRowIndex` attribute must, if the element has a parent `table`, `tbody`, `thead`, or `tfoot` element, return the index of the `tr` element in the parent element's `rows` collection (for tables, that's the `HTMLTableElement.rows` collection; for table sections, that's the `HTMLTableRowElement.rows` collection). If there is no such parent element, then the attribute must return −1.

The `cells` attribute must return an `HTMLCollection` rooted at the `tr` element, whose filter matches only `td` and `th` elements that are children of the `tr` element.

The `insertCell(index)` method must act as follows:

If index is less than −1 or greater than the number of elements in the `cells` collection, the method must throw an `IndexSizeError` exception.

If index is equal to −1 or equal to the number of items in `cells` collection, the method must create a `td` element, append it to the `tr` element, and return the newly created `td` element.

Otherwise, the method must create a `td` element, insert it as a child of the `tr` element, immediately before the indexth `td` or `th` element in the `cells` collection, and finally must return the newly created `td` element.

The `deleteCell(index)` method must remove the indexth element in the `cells` collection from its parent. If index is less than zero or greater than or equal to the number of elements in the `cells` collection, the method must instead throw an `IndexSizeError` exception.

#### 4.9.9 The `td` element

Categories:
  Sectioning root.
Contexts in which this element can be used:
  As a child of a `tr` element.
Content model:
  Flow content.
Tag omission in text/html:
  A `td` element's end tag can be omitted if the `td` element is immediately followed by a `td` or `th` element, or if there is no more content in the parent element.
Content attributes:
  Global attributes
  `colspan` — Number of columns that the cell is to span
  `rowspan` — Number of rows that the cell is to span
  `headers` — The header cells for this cell
DOM interface:

      interface HTMLTableDataCellElement : HTMLTableCellElement {};

The `td` element represents a data cell in a table.

The `td` element and its `colspan`, `rowspan`, and `headers` attributes take part in the table model.

User agents, especially in non-visual environments or where displaying the table as a 2D grid is impractical, may give the user context for the cell when rendering the contents of a cell; for instance, giving its position in the table model, or listing the cell's header cells (as determined by the algorithm for assigning header cells). When a cell's header cells are being listed, user agents may use the value of `abbr` attributes on those header cells, if any, instead of the contents of the header cells themselves.

In this example, we see a snippet of a Web application consisting of a grid of editable cells (essentially a simple spreadsheet). One of the cells has been configured to show the sum of the cells above it. Three have been marked as headings, which use `th` elements instead of `td` elements. A script would attach event handlers to these elements to maintain the total.

    <table>
     <tr>
      <th><input value="Name">
      <th><input value="Paid ($)">
     <tr>
      <td><input value="Jeff">
      <td><input value="14">
     <tr>
      <td><input value="Britta">
      <td><input value="9">
     <tr>
      <td><input value="Abed">
      <td><input value="25">
     <tr>
      <td><input value="Shirley">
      <td><input value="2">
     <tr>
      <td><input value="Annie">
      <td><input value="5">
     <tr>
      <td><input value="Troy">
      <td><input value="5">
     <tr>
      <td><input value="Pierce">
      <td><input value="1000">
     <tr>
      <th><input value="Total">
      <td><output value="1060">
    </table>

#### 4.9.10 The `th` element

Categories:
  If the `th` element is a sorting interface `th` element: Interactive content.
  Otherwise: None.
Contexts in which this element can be used:
  As a child of a `tr` element.
Content model:
  Flow content, but with no `header`, `footer`, sectioning content, or heading content descendants, and if the `th` element is a sorting interface `th` element, no interactive content descendants.
Tag omission in text/html:
  A `th` element's end tag can be omitted if the `th` element is immediately followed by a `td` or `th` element, or if there is no more content in the parent element.
Content attributes:
  Global attributes
  `colspan` — Number of columns that the cell is to span
  `rowspan` — Number of rows that the cell is to span
  `headers` — The header cells for this cell
  `scope` — Specifies which cells the header cell applies to
  `abbr` — Alternative label to use for the header cell when referencing the cell in other contexts
  `sorted` — Column sort direction and ordinality
DOM interface:

      interface HTMLTableHeaderCellElement : HTMLTableCellElement {
        attribute DOMString scope;
        attribute DOMString abbr;
        attribute DOMString sorted;
        void sort();
      };

The `th` element represents a header cell in a table.

The `th` element may have a `scope` content attribute specified. The `scope` attribute is an enumerated attribute with five states, four of which have explicit keywords:

The `row` keyword, which maps to the row state
  The row state means the header cell applies to some of the subsequent cells in the same row(s).
The `col` keyword, which maps to the column state
  The column state means the header cell applies to some of the subsequent cells in the same column(s).
The `rowgroup` keyword, which maps to the row group state
  The row group state means the header cell applies to all the remaining cells in the row group. A `th` element's `scope` attribute must not be in the row group state if the element is not anchored in a row group.
The `colgroup` keyword, which maps to the column group state
  The column group state means the header cell applies to all the remaining cells in the column group. A `th` element's `scope` attribute must not be in the column group state if the element is not anchored in a column group.
The auto state
  The auto state makes the header cell apply to a set of cells selected based on context.

The `scope` attribute's missing value default is the auto state.

The `th` element may have an `abbr` content attribute specified. Its value must be an alternative label for the header cell, to be used when referencing the cell in other contexts (e.g. when describing the header cells that apply to a data cell). It is typically an abbreviated form of the full header cell, but can also be an expansion, or merely a different phrasing.

The `sorted` attribute is used in the table sorting model.

The `th` element and its `colspan`, `rowspan`, `headers`, and `scope` attributes take part in the table model.

The `sort()` method is used in the table sorting model.

The `scope` IDL attribute must reflect the content attribute of the same name, limited to only known values.

The `abbr` and `sorted` IDL attributes must reflect the content attributes of the same name.

The following example shows how the `scope` attribute's `rowgroup` value affects which data cells a header cell applies to.

Here is a markup fragment showing a table:

    <table>
     <thead>
      <tr> <th> ID <th> Measurement <th> Average <th> Maximum
     <tbody>
      <tr> <td> <th scope=rowgroup> Cats <td> <td>
      <tr> <td> 93 <th scope=row> Legs <td> 3.5 <td> 4
      <tr> <td> 10 <th scope=row> Tails <td> 1 <td> 1
     <tbody>
      <tr> <td> <th scope=rowgroup> English speakers <td> <td>
      <tr> <td> 32 <th scope=row> Legs <td> 2.67 <td> 4
      <tr> <td> 35 <th scope=row> Tails <td> 0.33 <td> 1
    </table>

This would result in the following table:

ID | Measurement | Average | Maximum
--- | --- | --- | ---
| Cats |  |
93 | Legs | 3.5 | 4
10 | Tails | 1 | 1
| English speakers |  |
32 | Legs | 2.67 | 4
35 | Tails | 0.33 | 1

The headers in the first row all apply directly down to the rows in their column.

The headers with the explicit `scope` attributes apply to all the cells in their row group other than the cells in the first column.

The remaining headers apply just to the cells to the right of them.

#### 4.9.11 Attributes common to `td` and `th` elements

The `td` and `th` elements may have a `colspan` content attribute specified, whose value must be a valid non-negative integer greater than zero.

The `td` and `th` elements may also have a `rowspan` content attribute specified, whose value must be a valid non-negative integer. For this attribute, the value zero means that the cell is to span all the remaining rows in the row group.

These attributes give the number of columns and rows respectively that the cell is to span. These attributes must not be used to overlap cells, as described in the description of the table model.

The `td` and `th` element may have a `headers` content attribute specified. The `headers` attribute, if specified, must contain a string consisting of an unordered set of unique space-separated tokens that are case-sensitive, each of which must have the value of an ID of a `th` element taking part in the same table as the `td` or `th` element (as defined by the table model).

A `th` element with ID id is said to be directly targeted by all `td` and `th` elements in the same table that have `headers` attributes whose values include as one of their tokens the ID id. A `th` element A is said to be targeted by a `th` or `td` element B if either A is directly targeted by B or if there exists an element C that is itself targeted by the element B and A is directly targeted by C.

A `th` element must not be targeted by itself.

The `colspan`, `rowspan`, and `headers` attributes take part in the table model.

The `td` and `th` elements implement interfaces that inherit from the `HTMLTableCellElement` interface:

    interface HTMLTableCellElement : HTMLElement {
      attribute unsigned long colSpan;
      attribute unsigned long rowSpan;
      [PutForwards=value] readonly attribute DOMSettableTokenList headers;
      readonly attribute long cellIndex;
    };

cell . `cellIndex`

  Returns the position of the cell in the row's `cells` list. This does not necessarily correspond to the x-position of the cell in the table, since earlier cells might cover multiple rows or columns.

  Returns −1 if the element isn't in a row.

The `colSpan` IDL attribute must reflect the `colspan` content attribute. Its default value is 1.

The `rowSpan` IDL attribute must reflect the `rowspan` content attribute. Its default value is 1.

The `headers` IDL attribute must reflect the content attribute of the same name.

The `cellIndex` IDL attribute must, if the element has a parent `tr` element, return the index of the cell's element in the parent element's `cells` collection. If there is no such parent element, then the attribute must return −1.

#### 4.9.12 Processing model

The various table elements and their content attributes together define the table model.

A table consists of cells aligned on a two-dimensional grid of slots with coordinates (x, y). The grid is finite, and is either empty or has one or more slots. If the grid has one or more slots, then the x coordinates are always in the range 0 ≤ x < xwidth, and the y coordinates are always in the range 0 ≤ y < yheight. If one or both of xwidth and yheight are zero, then the table is empty (has no slots). Tables correspond to `table` elements.

A cell is a set of slots anchored at a slot (cellx, celly), and with a particular width and height such that the cell covers all the slots with coordinates (x, y) where cellx ≤ x < cellx+width and celly ≤ y < celly+height. Cells can either be data cells or header cells. Data cells correspond to `td` elements, and header cells correspond to `th` elements. Cells of both types can have zero or more associated header cells.

It is possible, in certain error cases, for two cells to occupy the same slot.

A row is a complete set of slots from x=0 to x=xwidth-1, for a particular value of y. Rows usually correspond to `tr` elements, though a row group can have some implied rows at the end in some cases involving cells spanning multiple rows.

A column is a complete set of slots from y=0 to y=yheight-1, for a particular value of x. Columns can correspond to `col` elements. In the absence of `col` elements, columns are implied.

A row group is a set of rows anchored at a slot (0, groupy) with a particular height such that the row group covers all the slots with coordinates (x, y) where 0 ≤ x < xwidth and groupy ≤ y < groupy+height. Row groups correspond to `tbody`, `thead`, and `tfoot` elements. Not every row is necessarily in a row group.

A column group is a set of columns anchored at a slot (groupx, 0) with a particular width such that the column group covers all the slots with coordinates (x, y) where groupx ≤ x < groupx+width and 0 ≤ y < yheight. Column groups correspond to `colgroup` elements. Not every column is necessarily in a column group.

Row groups cannot overlap each other. Similarly, column groups cannot overlap each other.

A cell cannot cover slots that are from two or more row groups. It is, however, possible for a cell to be in multiple column groups. All the slots that form part of one cell are part of zero or one row groups and zero or more column groups.

In addition to cells, columns, rows, row groups, and column groups, tables can have a `caption` element associated with them. This gives the table a heading, or legend.

A table model error is an error with the data represented by `table` elements and their descendants. Documents must not have table model errors.

##### 4.9.12.1 Forming a table

To determine which elements correspond to which slots in a table associated with a `table` element, to determine the dimensions of the table (xwidth and yheight), and to determine if there are any table model errors, user agents must use the following algorithm:

1. Let xwidth be zero.

2. Let yheight be zero.

3. Let pending `tfoot` elements be a list of `tfoot` elements, initially empty.

4. Let the table be the table represented by the `table` element. The xwidth and yheight variables give the table's dimensions. The table is initially empty.

5. If the `table` element has no children elements, then return the table (which will be empty), and abort these steps.

6. Associate the first `caption` element child of the `table` element with the table. If there are no such children, then it has no associated `caption` element.

7. Let the current element be the first element child of the `table` element.

   If a step in this algorithm ever requires the current element to be advanced to the next child of the `table` when there is no such next child, then the user agent must jump to the step labeled end, near the end of this algorithm.

8. While the current element is not one of the following elements, advance the current element to the next child of the `table`:

   - `colgroup`
   - `thead`
   - `tbody`
   - `tfoot`
   - `tr`

9. If the current element is a `colgroup`, follow these substeps:

   1. Column groups: Process the current element according to the appropriate case below:

      If the current element has any `col` element children

        Follow these steps:

        1. Let xstart have the value of xwidth.

        2. Let the current column be the first `col` element child of the `colgroup` element.

        3. Columns: If the current column `col` element has a `span` attribute, then parse its value using the rules for parsing non-negative integers.

           If the result of parsing the value is not an error or zero, then let span be that value.

           Otherwise, if the `col` element has no `span` attribute, or if trying to parse the attribute's value resulted in an error or zero, then let span be 1.

        4. Increase xwidth by span.

        5. Let the last span columns in the table correspond to the current column `col` element.

        6. If current column is not the last `col` element child of the `colgroup` element, then let the current column be the next `col` element child of the `colgroup` element, and return to the step labeled columns.

        7. Let all the last columns in the table from x=xstart to x=xwidth-1 form a new column group, anchored at the slot (xstart, 0), with width xwidth-xstart, corresponding to the `colgroup` element.

      If the current element has no `col` element children

        1. If the `colgroup` element has a `span` attribute, then parse its value using the rules for parsing non-negative integers.

           If the result of parsing the value is not an error or zero, then let span be that value.

           Otherwise, if the `colgroup` element has no `span` attribute, or if trying to parse the attribute's value resulted in an error or zero, then let span be 1.

        2. Increase xwidth by span.

        3. Let the last span columns in the table form a new column group, anchored at the slot (xwidth-span, 0), with width span, corresponding to the `colgroup` element.

   2. Advance the current element to the next child of the `table`.

   3. While the current element is not one of the following elements, advance the current element to the next child of the `table`:

      - `colgroup`
      - `thead`
      - `tbody`
      - `tfoot`
      - `tr`

   4. If the current element is a `colgroup` element, jump to the step labeled column groups above.

10. Let ycurrent be zero.

11. Let the list of downward-growing cells be an empty list.

12. Rows: While the current element is not one of the following elements, advance the current element to the next child of the `table`:

    - `thead`
    - `tbody`
    - `tfoot`
    - `tr`

13. If the current element is a `tr`, then run the algorithm for processing rows, advance the current element to the next child of the `table`, and return to the step labeled rows.

14. Run the algorithm for ending a row group.

15. If the current element is a `tfoot`, then add that element to the list of pending `tfoot` elements, advance the current element to the next child of the `table`, and return to the step labeled rows.

16. The current element is either a `thead` or a `tbody`.

    Run the algorithm for processing row groups.

17. Advance the current element to the next child of the `table`.

18. Return to the step labeled rows.

19. End: For each `tfoot` element in the list of pending `tfoot` elements, in tree order, run the algorithm for processing row groups.

20. If there exists a row or column in the table containing only slots that do not have a cell anchored to them, then this is a table model error.

21. Return the table.

The algorithm for processing row groups, which is invoked by the set of steps above for processing `thead`, `tbody`, and `tfoot` elements, is:

1. Let ystart have the value of yheight.

2. For each `tr` element that is a child of the element being processed, in tree order, run the algorithm for processing rows.

3. If yheight > ystart, then let all the last rows in the table from y=ystart to y=yheight-1 form a new row group, anchored at the slot with coordinate (0, ystart), with height yheight-ystart, corresponding to the element being processed.

4. Run the algorithm for ending a row group.

The algorithm for ending a row group, which is invoked by the set of steps above when starting and ending a block of rows, is:

1. While ycurrent is less than yheight, follow these steps:

   1. Run the algorithm for growing downward-growing cells.

   2. Increase ycurrent by 1.

2. Empty the list of downward-growing cells.

The algorithm for processing rows, which is invoked by the set of steps above for processing `tr` elements, is:

1. If yheight is equal to ycurrent, then increase yheight by 1. (ycurrent is never greater than yheight.)

2. Let xcurrent be 0.

3. Run the algorithm for growing downward-growing cells.

4. If the `tr` element being processed has no `td` or `th` element children, then increase ycurrent by 1, abort this set of steps, and return to the algorithm above.

5. Let current cell be the first `td` or `th` element child in the `tr` element being processed.

6. Cells: While xcurrent is less than xwidth and the slot with coordinate (xcurrent, ycurrent) already has a cell assigned to it, increase xcurrent by 1.

7. If xcurrent is equal to xwidth, increase xwidth by 1. (xcurrent is never greater than xwidth.)

8. If the current cell has a `colspan` attribute, then parse that attribute's value, and let colspan be the result.

   If parsing that value failed, or returned zero, or if the attribute is absent, then let colspan be 1, instead.

9. If the current cell has a `rowspan` attribute, then parse that attribute's value, and let rowspan be the result.

   If parsing that value failed or if the attribute is absent, then let rowspan be 1, instead.

10. If rowspan is zero and the `table` element's node document is not set to quirks mode, then let cell grows downward be true, and set rowspan to 1. Otherwise, let cell grows downward be false.

11. If xwidth < xcurrent+colspan, then let xwidth be xcurrent+colspan.

12. If yheight < ycurrent+rowspan, then let yheight be ycurrent+rowspan.

13. Let the slots with coordinates (x, y) such that xcurrent ≤ x < xcurrent+colspan and ycurrent ≤ y < ycurrent+rowspan be covered by a new cell c, anchored at (xcurrent, ycurrent), which has width colspan and height rowspan, corresponding to the current cell element.

    If the current cell element is a `th` element, let this new cell c be a header cell; otherwise, let it be a data cell.

    To establish which header cells apply to the current cell element, use the algorithm for assigning header cells described in the next section.

    If any of the slots involved already had a cell covering them, then this is a table model error. Those slots now have two cells overlapping.

14. If cell grows downward is true, then add the tuple {c, xcurrent, colspan} to the list of downward-growing cells.

15. Increase xcurrent by colspan.

16. If current cell is the last `td` or `th` element child in the `tr` element being processed, then increase ycurrent by 1, abort this set of steps, and return to the algorithm above.

17. Let current cell be the next `td` or `th` element child in the `tr` element being processed.

18. Return to the step labeled cells.

When the algorithms above require the user agent to run the algorithm for growing downward-growing cells, the user agent must, for each {cell, cellx, width} tuple in the list of downward-growing cells, if any, extend the cell cell so that it also covers the slots with coordinates (x, ycurrent), where cellx ≤ x < cellx+width.

##### 4.9.12.2 Forming relationships between data cells and header cells

Each cell can be assigned zero or more header cells. The algorithm for assigning header cells to a cell principal cell is as follows.

1. Let header list be an empty list of cells.

2. Let (principalx, principaly) be the coordinate of the slot to which the principal cell is anchored.

3. If the principal cell has a `headers` attribute specified

     1. Take the value of the principal cell's `headers` attribute and split it on spaces, letting id list be the list of tokens obtained.

     2. For each token in the id list, if the first element in the `Document` with an ID equal to the token is a cell in the same table, and that cell is not the principal cell, then add that cell to header list.

   If principal cell does not have a `headers` attribute specified

     1. Let principalwidth be the width of the principal cell.

     2. Let principalheight be the height of the principal cell.

     3. For each value of y from principaly to principaly+principalheight-1, run the internal algorithm for scanning and assigning header cells, with the principal cell, the header list, the initial coordinate (principalx,y), and the increments Δx=−1 and Δy=0.

     4. For each value of x from principalx to principalx+principalwidth-1, run the internal algorithm for scanning and assigning header cells, with the principal cell, the header list, the initial coordinate (x,principaly), and the increments Δx=0 and Δy=−1.

     5. If the principal cell is anchored in a row group, then add all header cells that are row group headers and are anchored in the same row group with an x-coordinate less than or equal to principalx+principalwidth-1 and a y-coordinate less than or equal to principaly+principalheight-1 to header list.

     6. If the principal cell is anchored in a column group, then add all header cells that are column group headers and are anchored in the same column group with an x-coordinate less than or equal to principalx+principalwidth-1 and a y-coordinate less than or equal to principaly+principalheight-1 to header list.

4. Remove all the empty cells from the header list.

5. Remove any duplicates from the header list.

6. Remove principal cell from the header list if it is there.

7. Assign the headers in the header list to the principal cell.

The internal algorithm for scanning and assigning header cells, given a principal cell, a header list, an initial coordinate (initialx, initialy), and Δx and Δy increments, is as follows:

1. Let x equal initialx.

2. Let y equal initialy.

3. Let opaque headers be an empty list of cells.

4. If principal cell is a header cell

     Let in header block be true, and let headers from current header block be a list of cells containing just the principal cell.

   Otherwise

     Let in header block be false and let headers from current header block be an empty list of cells.

5. Loop: Increment x by Δx; increment y by Δy.

   For each invocation of this algorithm, one of Δx and Δy will be −1, and the other will be 0.

6. If either x or y is less than 0, then abort this internal algorithm.

7. If there is no cell covering slot (x, y), or if there is more than one cell covering slot (x, y), return to the substep labeled loop.

8. Let current cell be the cell covering slot (x, y).

9. If current cell is a header cell

     1. Set in header block to true.

     2. Add current cell to headers from current header block.

     3. Let blocked be false.

     4. If Δx is 0

          If there are any cells in the opaque headers list anchored with the same x-coordinate as the current cell, and with the same width as current cell, then let blocked be true.

          If the current cell is not a column header, then let blocked be true.

        If Δy is 0

          If there are any cells in the opaque headers list anchored with the same y-coordinate as the current cell, and with the same height as current cell, then let blocked be true.

          If the current cell is not a row header, then let blocked be true.

     5. If blocked is false, then add the current cell to the headers list.

   If current cell is a data cell and in header block is true

     Set in header block to false. Add all the cells in headers from current header block to the opaque headers list, and empty the headers from current header block list.

10. Return to the step labeled loop.

A header cell anchored at the slot with coordinate (x, y) with width width and height height is said to be a column header if any of the following conditions are true:

- The cell's `scope` attribute is in the column state, or
- The cell's `scope` attribute is in the auto state, and there are no data cells in any of the cells covering slots with y-coordinates y .. y+height-1.

A header cell anchored at the slot with coordinate (x, y) with width width and height height is said to be a row header if any of the following conditions are true:

- The cell's `scope` attribute is in the row state, or
- The cell's `scope` attribute is in the auto state, the cell is not a column header, and there are no data cells in any of the cells covering slots with x-coordinates x .. x+width-1.

A header cell is said to be a column group header if its `scope` attribute is in the column group state.

A header cell is said to be a row group header if its `scope` attribute is in the row group state.

A cell is said to be an empty cell if it contains no elements and its text content, if any, consists only of White_Space characters.

#### 4.9.13 Table sorting model

The `sortable` attribute on `table` elements is a boolean attribute. When present, it indicates that the user agent is to allow the user to sort the `table`.

To make a column sortable in a `table` with a `thead`, the column needs to have `th` element that does not span multiple columns in a `thead` above any rows that it is to sort.

To make a column sortable in a `table` without a `thead`, the column needs to have `th` element that does not span multiple columns in the first `tr` element of the `table`, where that `tr` element is not in a `tfoot`.

When the user selects a column by which to sort, the user agent sets the `th` element's `sorted` attribute. This attribute can also be set manually, to indicate that the table should be automatically sorted, even when scripts modify the page on when the page is loaded.

The `sorted` attribute, if specified, must have a value that is a set of space-separated tokens consisting of optionally a token whose value is an ASCII case-insensitive match for the string "`reversed`", and optionally a token whose value is a valid non-negative integer greater than zero, in either order.

In other words, ignoring spaces and case, the `sorted` attribute's value can be empty, "`reversed`", "`1`", "`reversed 1`", or "`1 reversed`", where "1" is any number equal to or greater than 1.

While one or more `th` elements in the table have a `sorted` attribute, the user agent will keep the table's data rows sorted. The value of the attribute controls how the column is used in determining the sort order. The `reversed` keyword means that the column sort direction is reversed, rather than normal, which is the default if the keyword is omitted. The number, if present, indicates the column key ordinality; if the number is omitted, the column is the primary key, as if the value 1 had been specified.

Thus, `sorted="1"` indicates the table's primary key, `sorted="2"` its secondary key, and so forth.

A sorting-capable `th` element is a `th` element that matches all the following conditions simultaneously:

- It corresponds to a cell whose width is 1. (Specifically, a header cell, since this is a `th` element.)

- There is no cell that corresponds to another sorting-capable `th` element that covers slots in the same column but on a higher (earlier) row.

- If the cell's table has a row group corresponding to a `thead` element, the cell is in a row group that corresponds to the first `thead` element of the cell's table.

  Otherwise: the cell is not in a row group corresponding to a `tfoot` element, and the cell is in the first row of the table.

In other words, each column can have one sorting-capable `th` element; this will be the highest `th` in a `thead` that spans no other columns, or, if there is no `thead`, the `th` in the first row (that is not in a `tfoot`), assuming it spans no columns.

The sorting-capable `th` elements of the `table` element table are the sorting-capable `th` elements whose cell's table is table.

A `table` element table is a sorting-capable `table` element if there are one or more sorting-capable `th` elements of the `table` element table.

A `th` element is a sorting-enabled `th` element if it is a sorting-capable `th` element and it has a `sorted` attribute.

The sorting-enabled `th` elements of the `table` element table are the sorting-enabled `th` elements whose cell's table is table.

A `table` element table is a sorting-enabled `table` element if there are one or more sorting-capable `th` elements of the `table` element table, and at least one of them is a sorting-enabled `th` element (i.e. at least one has a `sorted` attribute).

A `table` element is a `table` element with a user-agent exposed sorting interface if it is a sorting-capable `table` element and has a `sortable` attribute specified.

A sorting interface `th` element is a sorting-capable `th` element whose cell's table is a `table` element with a user-agent exposed sorting interface.

Each `table` element has a currently-sorting flag, which must initially be false.

The `sorted` attribute must not be specified on `th` elements that are not sorting-capable `th` elements. The `sortable` attribute must not be specified on `table` elements that are not sorting-capable `table` elements.

To determine a `th` element's `sorted` attribute's column sort direction and column key ordinality, user agents must use the following algorithm:

1. Let direction be normal.

2. Let have explicit direction be false.

3. Let ordinality be 1.

4. Let have explicit ordinality be false.

5. Let tokens be the result of splitting the attribute's value on spaces.

6. For each token token in tokens, run the appropriate steps from the following list:

   If have explicit direction is false and token is an ASCII case-insensitive match for the string "`reversed`"

     Let direction be reversed and have explicit direction be true.

   If have explicit ordinality is false

     Parse token as an integer. If this resulted in an error or the value zero, then ignore the token. Otherwise, set ordinality to the parsed value, and set have explicit ordinality to true.

   Otherwise

     Ignore the token.

7. The column sort direction is the value of direction, and the column key ordinality is the value of ordinality.

A `table` must not have two `th` elements whose `sorted` attribute have the same column key ordinality.

The table sorting algorithm, which is applied to a `table`, is as follows:

1. Let table be the `table` element being sorted.

2. If table's currently-sorting flag is true, then abort these steps.

3. Set table's currently-sorting flag to true.

4. Fire a simple event named `sort` that is cancelable at table.

5. If the event fired in the previous step was canceled, then jump to the step labeled end below.

6. If table is not now a sorting-enabled `table` element, then jump to the step labeled end below.

   Even if table was a sorting-enabled `table` element when the algorithm was invoked, the DOM might have been entirely changed by the event handlers for the `sort` event, so this has to be verified at this stage, not earlier.

7. Let key heading cells be the sorting-enabled `th` elements of the `table` element table.

8. Sort key heading cells in ascending order of the column key ordinality of their `sorted` attributes, with those having the same column key ordinality being sorted in tree order.

9. Let row collection cursor be a pointer to an element, initially pointing at the first child of table that is after table's first `thead`, if any, and that is either a `tbody` or a `tr` element, assuming there is one. If there is no such child, then jump to the step labeled end below.

10. If table has no row group corresponding to a `thead` element, then set ignore first group to true. Otherwise, set it to false.

11. Run these substeps:

    1. Row loop: Let rows be an empty list of `tr` elements.

    2. Run these substeps:

       1. Run the appropriate steps from the following list:

          If row collection cursor points to a `tr` element

            1. Collect: Append the element pointed to by row collection cursor to rows.

            2. If there are no `tr` or `tbody` children of table that are later siblings of the element pointed to by row collection cursor, or if the next such child is a `tbody` element, then jump to the step labeled group below.

            3. Let row collection cursor point to the next `tr` child of table that is a later sibling of the element pointed to by row collection cursor.

            4. Jump back to the step labeled collect above.

          If row collection cursor points to a `tbody` element

            1. Place all the `tr` element children of the element pointed to by row collection cursor into rows, in tree order.

            2. If rows is empty, jump to the step labeled increment loop below.

       2. Group: Let groups be an empty list of groups of `tr` elements.

       3. Let group be an empty group of `tr` elements.

       4. Let group cursor be a pointer to an element, initially pointing at the first `tr` element in rows.

       5. Run these substeps:

          1. Start group: Let pending rows in group be 1.

          2. Run these substeps:

             1. Group loop: Append the `tr` element pointed to by group cursor to group.

             2. If there are any cells whose highest row's element is the one pointed to by group cursor, then let tallest height be the number of rows covered by the tallest such cell.

             3. If tallest height is greater than pending rows in group then set pending rows in group to tallest height.

             4. Decrement pending rows in group by one.

             5. Let group cursor point to the next `tr` element in rows, if any; otherwise, let it be null.

             6. If group cursor is not null and pending rows in group is not zero, jump back to the step labeled group loop.

          3. Append a new group to groups consisting of the `tr` elements in group.

          4. Empty group.

          5. If group cursor is not null, then jump back to the step labeled start group.

       6. If ignore first group is true, then drop the first group in groups and set ignore first group to false.

       7. Run these steps:

          1. Drop leading header groups: If groups is now empty, jump to the step labeled increment loop below.

          2. If the first group of groups consists of `tr` elements whose element children are all `th` elements, then drop the first group in groups and jump back to the previous step (labeled drop leading header groups).

       8. Let insertion point be a placeholder in a DOM tree, which can be used to reinsert nodes at a specific point in the DOM. Insert insertion point into the parent of the first `tr` element of the first group in groups, immediately before that `tr` element.

       9. Sort the groups in groups, using the following algorithm to decide the relative order of any two groups a and b (the algorithm either returns that a comes before b, or that b comes before a):

          1. Let key index be an index into key heading cells, initially denoting the first element in the list.

          2. Let direction be a sort direction, initially ascending. Its other possible value is descending. When direction is toggled, that means that if its value is ascending, it must be changed to descending, and when its value is descending, it must be changed to ascending.

          3. Run these substeps:

             1. Column loop: Let th be the key indexth `th` in key heading cells.

             2. If th's `sorted` attribute's column sort direction is reversed, then toggle direction.

             3. Let tentative order be the result of comparing two row groups using the `th` element th, with a and b as the rows.

             4. If tentative order is not "equal", then jump to the step labeled return below.

             5. Increment key index.

             6. If key index still denotes a `th` element in key heading cells, then jump back to the step above labeled column loop.

          4. If a's `tr` elements precede b's in tree order, then let tentative order be "a before b". Otherwise, let tentative order be "b before a".

          5. Return: Return the relative order given by the matching option from the following list:

             If direction is ascending and tentative order is "a before b"
               Return that a comes before b.
             If direction is ascending and tentative order is "b before a"
               Return that b comes before a.
             If direction is descending and tentative order is "a before b"
               Return that b comes before a.
             If direction is descending and tentative order is "b before a"
               Return that a comes before b.

          When the user agent is required to compare two row groups using the `th` element th, with a and b being the two row groups respectively, the user agent must run the following steps:

          1. Let x be the x-coordinate of the slots that `th` covers in its table.

          2. Let cella be the element corresponding to the cell in the first row of group a that covers the slot in that row whose x-coordinate is x.

             Let cellb be the element corresponding to the cell in the first row of group b that covers the slot in that row whose x-coordinate is x.

             In either case, if there's no cell that actually covers the slot, then use the value null instead.

          3. Let typea and valuea be the type and value of the cell cella, as defined below.

             Let typeb and valueb be the type and value of the cell cellb, as defined below.

             The type and value of the cell cell are computed as follows.

             1. If cell is null, then the type is "string" and the value is the empty string; abort these steps.

             2. If, ignoring inter-element whitespace and nodes other than Element and Text nodes, cell has only one child and that child is a `data` element, then the value is the value of that `data` element's `value` attribute, if there is one, or the empty string otherwise; the type is "string".

             3. If, ignoring inter-element whitespace and nodes other than Element and Text nodes, cell has only one child and that child is a `progress` element, then the value is the value of that `progress` element's `value` attribute, if there is one, or the empty string otherwise; the type is "string".

             4. If, ignoring inter-element whitespace and nodes other than Element and Text nodes, cell has only one child and that child is a `meter` element, then the value is the value of that `meter` element's `value` attribute, if there is one, or the empty string otherwise; the type is "string".

             5. If, ignoring inter-element whitespace and nodes other than Element and Text nodes, cell has only one child and that child is a `time` element, then the value is the machine-readable equivalent of the element's contents, if any, and the type is the kind of value that is thus obtained (a month, a date, a yearless date, a time, a local date and time, a time-zone offset, a global date and time, a week, a year, or a duration); abort these steps after completing this one.

                If there is no machine-readable equivalent, then the type is "string" and the value is the empty string.

                If the type is a month, a date, a week, or a year, then change the value to be the instant in time (with no time zone) that describes the earliest moment that the value represents, and change the type to be a local date and time.

                For example, if the cell was `<td><time>2011-11</time>` then for sorting purposes the value is interpreted as "2011-11-01T00:00:00.000" and the type is treated as a local date and time rather than a month.

                Similarly, if the cell was `<td><time datetime="2014">MMXIV</time>` then for sorting purposes the value is interpreted as "2014-01-01T00:00:00.000" and the type is treated as a local date and time rather than a year.

             6. The value is the element's `textContent`. The type is "string".

          4. If typea and typeb are not equal, then: return "a before b" if typea is earlier in the following list than typeb, otherwise, return "b before a"; then, abort these steps.

             1. time
             2. yearless date
             3. local date and time
             4. global date and time
             5. time-zone offset
             6. duration
             7. "string"

          5. If valuea and valueb are equal, then return "equal" and abort these steps.

          6. If typea and typeb are not "string", then: if valuea is earlier than valueb then return "a before b" and abort these steps, otherwise, return "b before a" and abort these steps.

             Values sort in their natural order, with the following additional constraints:

             For time values, 00:00:00.000 is the earliest value and 23:59:59.999 is the latest value.

             For yearless date values, 01-01 is the earliest value and 12-31 is the latest value; 02-28 is earlier than 02-29 which is earlier than 03-01.

             Values that are local date and time compare as if they were in the same time zone.

             For time-zone offset values, -23:59 is the earliest value and +23:59 is the latest value.

          7. Let componentsa be the result of parsing the sort key valuea.

             Let componentsb be the result of parsing the sort key valueb.

             As described below, componentsa and componentsb are tuples consisting of a list of n numbers, a list of n number strings, a list of n+1 non-numeric strings, and a list of 2n+1 raw strings, for any non-negative integer value of n (zero or more).

          8. Let order be the result of a locale-specific string comparison of componentsa's first non-numeric string and componentsb's first non-numeric string, in the context of th.

             If order is not "equal" then return order and abort these steps.

          9. If componentsa and componentsb both have exactly one number, then run these substeps:

             1. If componentsa's number is less than componentsb's number, return "a before b".

                If componentsb's number is less than componentsa's number, return "b before a".

             2. Let order be the result of a locale-specific string comparison of componentsa's second non-numeric string and componentsb's second non-numeric string, in the context of th.

                If order is not "equal" then return order and abort these steps.

             3. Let order be the result of a locale-specific string comparison of componentsa's number string and componentsb's number string, in the context of th.

                If order is not "equal" then return order and abort these steps.

             Otherwise, run these substeps:

             1. If componentsa has zero numbers but componentsb has more than zero numbers, return "a before b".

                If componentsb has zero numbers but componentsa has more than zero numbers, return "b before a".

             2. If componentsa has one number, return "a before b".

                If componentsb has one number, return "b before a".

             3. If componentsa and componentsb have more than one number, run these substeps:

                1. Let count be the smaller of the number of numbers in componentsa and the number of numbers in componentsb.

                2. For each number in componentsa and componentsb from the first to the countth, in order: if componentsa's number is less than componentsb's number, then return "a before b" and abort these steps; otherwise, if componentsb's number is less than componentsa's number, return "b before a" and abort these steps.

                3. If componentsa has fewer numbers than componentsb, return "a before b" and abort these steps.

                   If componentsb has fewer numbers than componentsa, return "b before a" and abort these steps.

                4. Let index be zero.

                5. String loop: Let order be the result of a locale-specific string comparison of componentsa's indexth number string and componentsb's indexth number string, in the context of th.

                   If order is not "equal" then return order and abort these steps.

                6. Increment index.

                7. Let order be the result of a locale-specific string comparison of componentsa's indexth separator string and componentsb's indexth separator string, in the context of th.

                   If order is not "equal" then return order and abort these steps.

                8. If index is less than the number of numbers in componentsa and componentsb, jump back to the step labeled string loop.

          10. Let index be zero.

          11. Run these substeps:

              1. Final loop: Let order be the result of a raw string comparison of componentsa's nth raw string and componentsb's nth raw string.

                 If order is not "equal" then return order and abort these steps.

              2. Increment index.

              3. If index is less than the number of raw strings in componentsa and componentsb, jump back to the step labeled final loop.

          12. Return "equal".

       10. Let new order be a list of `tr` elements consisting of the `tr` elements of all the groups in the newly ordered groups, with the `tr` elements being in the same order as the groups to which they belong are in groups, and the `tr` elements within each such group themselves being ordered in tree order.

       11. Remove all the `tr` elements in new order from their parents, in tree order.

       12. Insert all the `tr` elements in new order into the DOM at the location of insertion point, in the order these elements are found in new order.

       13. Remove insertion point from the DOM.

    3. Increment loop: If there are no `tr` or `tbody` children of table that are later siblings of the element pointed to by row collection cursor, then jump to the step labeled end below.

    4. Let row collection cursor point to the next `tr` or `tbody` child of table that is a later sibling of the element pointed to by row collection cursor.

    5. Jump back to the step labeled row loop above.

12. End: Set table's currently-sorting flag to false.

When a user agent is to parse the sort key value, it must run the following steps. These return a tuple consisting of a list of n numbers, a list of n number strings, a list of n+1 non-numeric strings, and a list of 2n+1 raw strings, respectively, for any non-negative integer value of n (zero or more).

1. Let raw strings be a list of strings initially containing just one entry, an empty string.

2. Let negatives prejudiced be false.

   Let decimals prejudiced be false.

   Let exponents prejudiced be false.

3. Let buffer be the empty string.

   Let index be zero.

   Let mode be "separator".

   When a subsequent step in this algorithm says to push the buffer, the user agent must run the following substeps:

   1. Add an entry to raw strings that consists of the value of buffer.

   2. Add an entry to raw strings that is the empty string.

   3. Decrement index by one.

   4. Set mode to "separator".

4. Let checkpoint buffer be the empty string.

   Let checkpoint index be zero.

   When a subsequent step in this algorithm says to checkpoint, the user agent must run the following substeps:

   1. Set the checkpoint buffer to the value of buffer.

   2. Set the checkpoint index to the value of index.

   When a subsequent step in this algorithm says to push the checkpoint, the user agent must run the following substeps:

   1. Add an entry to raw strings that consists of the value of checkpoint buffer.

   2. Add an entry to raw strings that is the empty string.

   3. Decrement index by one.

   4. Set mode to "separator".

5. Run through the following steps repeatedly until the condition in the last step is met.

   1. Top of loop: If index is equal to or greater than the number of characters in value, let c be EOF. Otherwise, let c be the indexth character in value.

   2. Run the appropriate steps from the following list:

      If mode is "separator"

        Run the appropriate substeps from the following list:

        If c is a space character

          Set negatives prejudiced to false.

          Set decimals prejudiced to false.

          Set exponents prejudiced to false.

          Append c to the last entry in raw strings.

        If c is a U+002D HYPHEN-MINUS character (-) and negatives prejudiced is false

          Set buffer to the value of c.

          Set mode to "negative".

        If c is a U+002E FULL STOP character (.) and decimals prejudiced is false

          Set buffer to the value of c.

          Set mode to "leading-decimal".

        If c is an ASCII digit

          Set buffer to the value of c.

          Set mode to "integral".

        If c is an uppercase ASCII letter or a lowercase ASCII letter

          Set exponents prejudiced to true.

          Append c to the last entry in raw strings.

        If c is EOF

          Do nothing.

        Otherwise

          Append c to the last entry in raw strings.

      If mode is "negative"

        Run the appropriate substeps from the following list:

        If c is a U+002D HYPHEN-MINUS character (-)

          Set negatives prejudiced to true.

          Append buffer to the last entry in raw strings.

          Append c to the last entry in raw strings.

          Set mode to "separator".

        If c is a U+002E FULL STOP character (.) and decimals prejudiced is false

          Append c to buffer.

          Set mode to "leading-decimal".

        If c is an ASCII digit

          Append c to buffer.

          Set mode to "integral".

        Otherwise

          Append buffer to the last entry in raw strings.

          Decrement index by one.

          Set mode to "separator".

      If mode is "integral"

        Run the appropriate substeps from the following list:

        If c is a U+002D HYPHEN-MINUS character (-)

          Set negatives prejudiced to true.

          Push the buffer.

        If c is a U+002E FULL STOP character (.) and decimals prejudiced is false

          Checkpoint.

          Append c to buffer.

          Set mode to "decimal".

        If c is an ASCII digit

          Append c to the last entry in raw strings.

        If c is a U+0045 LATIN CAPITAL LETTER E character or a U+0065 LATIN SMALL LETTER E character and exponents prejudiced is false

          Checkpoint.

          Append c to buffer.

          Set mode to "exponent".

        Otherwise

          Push the buffer.

      If mode is "leading-decimal"

        Run the appropriate substeps from the following list:

        If c is an ASCII digit

          Append c to buffer.

          Set mode to "decimal".

        Otherwise

          Append buffer to the last entry in raw strings.

          Decrement index by one.

          Set mode to "separator".

      If mode is "decimal"

        Run the appropriate substeps from the following list:

        If c is a U+002D HYPHEN-MINUS character (-)

          Set negatives prejudiced to true.

          Push the buffer.

        If c is a U+002E FULL STOP character (.) and any of the characters in value past the indexth character are ASCII digits

          Set decimals prejudiced to true.

          Push the checkpoint.

        If c is a U+002E FULL STOP character (.) and none of the characters in value past the indexth character are ASCII digits

          Push the buffer.

        If c is an ASCII digit

          Append c to buffer.

        If c is a U+0045 LATIN CAPITAL LETTER E character or a U+0065 LATIN SMALL LETTER E character and exponents prejudiced is false

          Checkpoint.

          Append c to buffer.

          Set mode to "exponent".

        Otherwise

          Push the buffer.

      If mode is "exponent"

        Run the appropriate substeps from the following list:

        If c is a U+002D HYPHEN-MINUS character (-) and negatives prejudiced is false

          Append c to buffer.

          Set mode to "exponent-negative".

        If c is a U+002E FULL STOP character (.)

          Set decimals prejudiced to true.

          Push the checkpoint.

        If c is an ASCII digit

          Append c to buffer.

          Set mode to "exponent-number".

        If c is a U+0045 LATIN CAPITAL LETTER E character or a U+0065 LATIN SMALL LETTER E character

          Set exponents prejudiced to true.

          Push the checkpoint.

        Otherwise

          Push the checkpoint.

      If mode is "exponent-negative"

        Run the appropriate substeps from the following list:

        If c is a U+002D HYPHEN-MINUS character (-)

          Set negatives prejudiced to true.

          Push the checkpoint.

        If c is a U+002E FULL STOP character (.)

          Set decimals prejudiced to true.

          Push the checkpoint.

        If c is an ASCII digit

          Append c to buffer.

          Set mode to "exponent-negative-number".

        If c is a U+0045 LATIN CAPITAL LETTER E character or a U+0065 LATIN SMALL LETTER E character

          Set exponents prejudiced to true.

          Push the checkpoint.

        Otherwise

          Push the checkpoint.

      If mode is "exponent-number"

        Run the appropriate substeps from the following list:

        If c is a U+002D HYPHEN-MINUS character (-)

          Set negatives prejudiced to true.

          Push the buffer.

        If c is a U+002E FULL STOP character (.)

          Set decimals prejudiced to true.

          Push the checkpoint.

        If c is an ASCII digit

          Append c to buffer.

        If c is a U+0045 LATIN CAPITAL LETTER E character or a U+0065 LATIN SMALL LETTER E character

          Set exponents prejudiced to true.

          Push the checkpoint.

        Otherwise

          Push the buffer.

      If mode is "exponent-negative-number"

        Run the appropriate substeps from the following list:

        If c is a U+002D HYPHEN-MINUS character (-)

          Set negatives prejudiced to true.

          Push the checkpoint.

        If c is a U+002E FULL STOP character (.)

          Set decimals prejudiced to true.

          Push the checkpoint.

        If c is an ASCII digit

          Append c to buffer.

        If c is a U+0045 LATIN CAPITAL LETTER E character or a U+0065 LATIN SMALL LETTER E character

          Set exponents prejudiced to true.

          Push the checkpoint.

        Otherwise

          Push the buffer.

   3. Increment index by one.

   4. If index is greater than the number of characters in value, stop repeating these substeps and continue along the overall steps. Otherwise, return to the step labeled top of loop.

6. Let numbers be an empty list.

   Let number strings be an empty list.

   Let non-numeric strings be an empty list.

7. For each even-numbered entry in raw strings, in order, starting from the first entry (numbered 0), append an entry to non-numeric strings that consists of the result of trimming and collapsing the value of the entry.

8. If raw strings has more than one entry, then, for each odd-numbered entry in raw strings, in order, starting from the second entry (numbered 1), append an entry to number strings that consists of the value of the entry, and append an entry to number strings that consists of the result of parsing the value of the entry using the rules for parsing floating-point number values.

9. Return numbers, number strings, non-numeric strings, and raw strings respectively.

When the user agent is required by the step above to perform a locale-specific string comparison of two strings a and b in the context of an element e, the user agent must apply the Unicode Collation Algorithm, using the Default Unicode Collation Element Table as customised for the language of the element e in the Common Locale Data Repository, to the strings a and b, ignoring case. If the result of this algorithm places a first, then return "a before b"; if it places b first, then return "b before a"; otherwise, if they compare as equal, then return "equal". [UCA] [CLDR]

When the user agent is required by the step above to perform a raw string comparison of two strings a and b, the user agent must apply the Unicode Collation Algorithm, using the Default Unicode Collation Element Table without customizations, to the strings a and b. If the result of this algorithm places a first, then return "a before b"; if it places b first, then return "b before a"; otherwise, if they compare as equal, then return "equal". [UCA]

Where the steps above refer to trimming and collapsing a string value, it means running the following algorithm:

1. Strip leading and trailing whitespace from value.

2. Replace any sequence of one or more space characters in value with a single U+0020 SPACE character.

When any of the descendants of a sorting-enabled `table` element change in any way (including attributes changing), and when a `table` element becomes a sorting-enabled `table` element, the `table` element is said to become a table with a pending sort. When a `table` element becomes a table with a pending sort, the user agent must queue a microtask that applies the table sorting algorithm to that `table`, and then flags the `table` as no longer being a table with a pending sort.

When the user agent is to set the sort key to a `th` element target, it must run the following algorithm:

1. Let table be the `table` of the table of which target is a header cell.

2. If `th` is a sorting-enabled `th` element whose column key ordinality is 1, then: if its column sort direction is normal, set that element's `sorted` attribute to the string "`reversed`", otherwise, set it to the empty string; then, abort these steps.

3. Let current headers be the sorting-enabled `th` elements of the `table` element table, excluding target.

4. Sort current headers by their `sorted` attributes' column key ordinality, in ascending order, with elements that have the same column key ordinality being sorted in tree order.

5. Let level be 2.

6. For each `th` element th in current headers, in order, run the following substeps:

   1. If th's `sorted` attribute's column sort direction is normal, then set th's `sorted` attribute to a valid integer whose value is level. Otherwise, set it to the concatenation of the string "`reversed`", a U+0020 SPACE character, and a valid integer whose value is level.

   2. Increment level by 1.

7. Set target's `sorted` attribute to the empty string.

The activation behaviour of a sorting interface `th` element is to set the sort key to the `th` element.

The `table` will be sorted the next time the user agent performs a microtask checkpoint.

th . `sort`()

  Act as if the user had indicated that this was to be the new primary sort column.

  The `table` won't actually be sorted until the script terminates.

table . `stopSorting`()

  Removes all the `sorted` attributes that are causing the table to automatically sort its contents, if any.

The `th` element's `sort()` method, when invoked, must run the following steps:

1. If the `th` element is not a sorting-capable `th` element, then abort these steps.

2. Set the sort key to the `th` element.

   The `table` will be sorted the next time the user agent performs a microtask checkpoint.

The `table` element's `stopSorting()` method, when invoked, must remove the `sorted` attribute of all the sorting-enabled `th` elements of the table element on which the method was invoked.

#### 4.9.14 Examples

This section is non-normative.

The following shows how might one mark up the bottom part of table 45 of the Smithsonian physical tables, Volume 71:

    <table>
     <caption>Specification values: <b>Steel</b>, <b>Castings</b>,
     Ann. A.S.T.M. A27-16, Class B;* P max. 0.06; S max. 0.05.</caption>
     <thead>
      <tr>
       <th rowspan=2>Grade.</th>
       <th rowspan=2>Yield Point.</th>
       <th colspan=2>Ultimate tensile strength</th>
       <th rowspan=2>Per cent elong. 50.8mm or 2 in.</th>
       <th rowspan=2>Per cent reduct. area.</th>
      </tr>
      <tr>
       <th>kg/mm<sup>2</sup></th>
       <th>lb/in<sup>2</sup></th>
      </tr>
     </thead>
     <tbody>
      <tr>
       <td>Hard</td>
       <td>0.45 ultimate</td>
       <td>56.2</td>
       <td>80,000</td>
       <td>15</td>
       <td>20</td>
      </tr>
      <tr>
       <td>Medium</td>
       <td>0.45 ultimate</td>
       <td>49.2</td>
       <td>70,000</td>
       <td>18</td>
       <td>25</td>
      </tr>
      <tr>
       <td>Soft</td>
       <td>0.45 ultimate</td>
       <td>42.2</td>
       <td>60,000</td>
       <td>22</td>
       <td>30</td>
      </tr>
     </tbody>
    </table>

This table could look like this:

Specification values: Steel, Castings, Ann. A.S.T.M. A27-16, Class B;* P max. 0.06; S max. 0.05.
Grade. | Yield Point. | Ultimate tensile strength | Per cent elong. 50.8 mm or 2 in. | Per cent reduct. area.
--- | --- | --- | --- | ---
kg/mm2 | lb/in2
Hard | 0.45 ultimate | 56.2 | 80,000 | 15 | 20
Medium | 0.45 ultimate | 49.2 | 70,000 | 18 | 25
Soft | 0.45 ultimate | 42.2 | 60,000 | 22 | 30

The following shows how one might mark up the gross margin table on page 46 of Apple, Inc's 10-K filing for fiscal year 2008:

    <table>
     <thead>
      <tr>
       <th>
       <th>2008
       <th>2007
       <th>2006
     <tbody>
      <tr>
       <th>Net sales
       <td>$ 32,479
       <td>$ 24,006
       <td>$ 19,315
      <tr>
       <th>Cost of sales
       <td>  21,334
       <td>  15,852
       <td>  13,717
     <tbody>
      <tr>
       <th>Gross margin
       <td>$ 11,145
       <td>$  8,154
       <td>$  5,598
     <tfoot>
      <tr>
       <th>Gross margin percentage
       <td>34.3%
       <td>34.0%
       <td>29.0%
    </table>

This table could look like this:

| 2008 | 2007 | 2006
--- | --- | --- | ---
Net sales | $ 32,479 | $ 24,006 | $ 19,315
Cost of sales | 21,334 | 15,852 | 13,717
Gross margin | $ 11,145 | $ 8,154 | $ 5,598
Gross margin percentage | 34.3% | 34.0% | 29.0%

The following shows how one might mark up the operating expenses table from lower on the same page of that document:

    <table>
     <colgroup> <col>
     <colgroup> <col> <col> <col>
     <thead>
      <tr> <th> <th>2008 <th>2007 <th>2006
     <tbody>
      <tr> <th scope=rowgroup> Research and development
           <td> $ 1,109 <td> $ 782 <td> $ 712
      <tr> <th scope=row> Percentage of net sales
           <td> 3.4% <td> 3.3% <td> 3.7%
     <tbody>
      <tr> <th scope=rowgroup> Selling, general, and administrative
           <td> $ 3,761 <td> $ 2,963 <td> $ 2,433
      <tr> <th scope=row> Percentage of net sales
           <td> 11.6% <td> 12.3% <td> 12.6%
    </table>

This table could look like this:

| 2008 | 2007 | 2006
--- | --- | --- | ---
Research and development | $ 1,109 | $ 782 | $ 712
Percentage of net sales | 3.4% | 3.3% | 3.7%
Selling, general, and administrative | $ 3,761 | $ 2,963 | $ 2,433
Percentage of net sales | 11.6% | 12.3% | 12.6%

Sometimes, tables are used for dense data. For examples, here a table is used to show entries in an access log:

    <table sortable>
     <thead>
      <tr>
       <th sorted> Timestamp
       <th> IP
       <th> Message
     <tbody>
      <tr>
       <td> <time>21:01</time>
       <td> 128.30.52.199
       <td> Exceeded ingress limit
      <tr>
       <td> <time>21:04</time>
       <td> 128.30.52.3
       <td> Authentication failure
      <tr>
       <td> <time>22:35</time>
       <td> 128.30.52.29
       <td> Malware command request blocked
      <tr>
       <td> <time>22:36</time>
       <td> 128.30.52.3
       <td> Authentication failure
    </table>

Because the `table` element has a `sortable` attribute, the column headers can be selected to change the table's sort order.

This might render as follows:

If the user activates the second column, the table might change as follows:

If the user activates the second column again, reversing the sort order, it might change as follows: