Table with Expando Rows

I regularly work on projects with HTML tables that have been pushed to the edge with styles, scripts, and widget features. A common pattern is where rows are hidden until the user opts to show them. Unfortunately, the pattern is often over-complicated with unnecessary script and styles that regularly break the table semantics or fail to work across all contexts.

Typically there are only two things you as an author need to do for a row expando to retain table semantics (other than using a contiguous <table>, of course):

1. Make sure you use the table-row CSS display property instead of block, and
2. Use a disclosure widget as your toggle.

Example

You can visit the pen directly to fiddle with it, or view in debug mode to test it in your favorite AT (assistive technology).

Note this example is not responsive.

See the Pen Table with Expando Rows by Adrian Roselli (@aardrian) on CodePen.

Disclosure Widget

The disclosure widget is a native HTML <button>. If you read my post Link + Disclosure Widget Navigation, it goes into more detail than I will here.

Much like that example, the accessible name is concatenated from its own aria-label value and the text value in the relevant cell to provide a more natural name (eg: [n] more items from [author]). The aria-expanded value tells assistive technology whether the button has been expanded or not, and is also the hook we use for the styling.

[…]
    <tr>
      <td>
        <button type="button" id="btnMSb" aria-expanded="false" onclick="toggle(this.id,'#MS01b,#MS02b,#MS03b');" aria-controls="MS01b MS02b MS03b" aria-label="3 more from" aria-labelledby="btnMSb lblMSb">
          […]
        </button>
      </td>
      <td id="lblMSb">Mary Shelley</td>
[…]
    </tr>
[…]

The aria-controls value is a space-separated list of the ids of the rows you are affecting. Where aria-controls is supported, confirm that its announcement in screen readers (JAWS only today) is not too verbose for your users. If it is, you may want to remove it altogether. Its absence won’t result in a barrier, but it may make the widget easier to use for some users when useful screen reader support starts to appear.

The CSS

The easiest way to ensure the programmatic state of the button matches the visual styles is to use attribute selectors such as button[aria-expanded="true|false"]. The styles for both example tables only change the SVG.

.cell button[aria-expanded="true"] svg {
  transform: rotate(90deg);
}
.row button[aria-expanded="true"] svg {
  transform: rotate(180deg);
}

Your own styles will likely vary, of course.

The Script

The function is nothing special. It takes a list of ids and feeds them into a query selector, and it takes the id of the button as well. It checks then flips the aria-expanded value on the button while swapping the value of the class between shown and hidden.

If I could use adjacent sibling selectors (keying off the aria-expanded value) to toggle the visibility of the rows I would. The HTML table structure precludes that, which is the only reason I am using a class to do the work.

This is not production-ready script. It does, however, take Internet Explorer into account by not using classList.replace, which IE does not support.

function toggle(btnID, eIDs) {
  // Feed the list of ids as a selector
  var theRows = document.querySelectorAll(eIDs);
  // Get the button that triggered this
  var theButton = document.getElementById(btnID);
  // If the button is not expanded...
  if (theButton.getAttribute("aria-expanded") == "false") {
    // Loop through the rows and show them
    for (var i = 0; i < theRows.length; i++) {
      theRows[i].classList.add("shown");
      theRows[i].classList.remove("hidden");
    }
    // Now set the button to expanded
    theButton.setAttribute("aria-expanded", "true");
  // Otherwise button is not expanded...
  } else {
    // Loop through the rows and hide them
    for (var i = 0; i < theRows.length; i++) {
      theRows[i].classList.add("hidden");
      theRows[i].classList.remove("shown");
    }
    // Now set the button to collapsed
    theButton.setAttribute("aria-expanded", "false");
  }
}

At page load, the rows in my example are not hidden with inline CSS. Whether you hide or display them on initial load in the name of Progressive Enhancement is up to you and your use case. Either one can be a valid approach, but account for it in your function as well.

Tables

I made two tables so you could see two ways this might work. The full-row disclosure widget shows the text that is also announced to screen readers, and it provides a much larger hit area. As a column-spanning cell it can complicate table navigation for novice screen reader users but is much easier to find — you can stumble across it from any column.

The other example has the disclosure widget in its own column, arguably making it easier to avoid. It also warrants its own column header. The value is Toggle and I use a well-tested technique to visually hide it (partly because NVDA does not support the abbr attribute on <th>). See the visually-hidden class to steal the styles.

The HTML for the row is not complex. Just an id and a class, with the latter toggled via script.

    <tr id="EDENS02b" class="hidden">
      <td></td>
      <td>Emma Dorothy Eliza Nevitte Southworth</td>
      <td>Unknown; or the Mystery of Raven Rocks</td>
      <td>1889</td>
      <td></td>
      <td></td>
    </tr>

The CSS

The CSS for the two classes that adjust the display of the row is critical. If you use display: block instead of display: table-row then the browser drops all the semantics for the row and assistive technology cannot navigate it. See my post Tables, CSS Display Properties, and ARIA for more detail.

tr.shown, tr.hidden {
  background-color: #eee;
  display: table-row;
}

tr.hidden {
  display: none;
}

Screen Readers

Note that while a screen reader will not announce how many new rows are added (hence the accessible name to manage that expectation), once the new rows are visible the screen reader factors them into the total row count and user’s position within the table.

It is also important to ensure any new rows you add come after the control that makes them appear in the source order. Otherwise a screen reader use cannot be expected to know where they have appeared, let alone navigate around the table looking for them.

I have embedded some videos showing how a screen reader user might navigate the expando feature.

JAWS / IE11

NVDA / Firefox

VoiceOver / Safari

Update: 19 April 2020

Last week someone on Twitter proposed that it was impossible to animate a new row in a table and have it extend beyond the width of the table itself. This post was referenced in another tweet to show one approach.

Separately, the @keyframers made a pen to show their approach and dedicated an hour long YouTube video. To their credit, they kept the table semantics. I forked their pen (embedded below) and adjusted the buttons to act as true disclosure widgets and to ensure the newly-shown row would have correct a column header.

See the Pen Flipping Tables | Table animation challenge using FLIP | @keyframers 3.0 by Adrian Roselli (@aardrian) on CodePen.

Update: 9 May 2020

I evaluated a pattern recently that used aria-rowindex to try to artificially reposition rows inserted at the end of the table DOM into a position much earlier in the table by providing a value much lower than its actual position. Similarly, the value of aria-rowcount was being changed to reflect the new total number of rows once more were disclosed or hidden.

These are both wrong uses. These properties are intended to be used with tables that are paged, showing only a few rows at a time from a larger set. You use aria-rowcount to identify the total number of rows in a table, including those not yet available. You would use aria-rowindex to identify the current position within that total number of rows across pages.

If you have 83 results in a search and you show 20 per page, then the table would have aria-rowcount="84" (one for the header row). The third row on the third screen would have aria-rowindex="42" (because the first row is the header row).

The good news is that for the tables in this example you can ignore all this. If your users are having trouble keeping track in larger or more complex tables, then it may be worth trying these properties. If you have paged tables with expando rows, and you use these properties, then you will need to do sufficient testing with users to identify if accounting for the hidden rows in your aria-rowindex values is more of a hindrance or help.

From my own testing with paged tables that tell you how many results per page and how many total pages or results, then even with expando rows you can ignore aria-rowcount and aria-rowindex altogether.

Update: 29 September 2020

Léonie Watson has just posted How screen readers navigate data tables where she walks through a sample table to get some information, explaining each step, the keyboard commands, and the output. She also links to a video demonstration, which I have embedded below.