Accessible Expandable Tree Table In JavaScript

An accessible expandable HTML enhancement script that allows the user to toggle (expand/collapse) table rows just like a tree structure.

How to use it:

Add the class="hidden" to the table rows which should be hidden on init. Note that each tr must have a unique ID.

<tr id="MS01b" class="hidden">
  <td></td>
  <td>Mary Shelley</td>
  <td>Valperga: Or, the Life and Adventures of Castruccio, Prince of Lucca</td>
  <td>1823</td>
  <td></td>
  <td></td>
</tr>
<tr id="MS02b" class="hidden">
  <td></td>
  <td>Mary Shelley</td>
  <td>The Last Man</td>
  <td>1826</td>
  <td></td>
  <td></td>
</tr>
<tr id="MS03b" class="hidden">
  <td></td>
  <td>Mary Shelley</td>
  <td>The Fortunes of Perkin Warbeck, A Romance</td>
  <td>1830</td>
  <td></td>
  <td></td>
</tr>

Add a toggle button to the parent table row and specify the row IDs in the toggle method.

<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">
    <svg xmlns="\http://www.w3.org/2000/svg&quot;" viewBox="0 0 80 80" focusable="false"><path d="M70.3 13.8L40 66.3 9.7 13.8z"></path></svg>
  </button>
</td>

The required CSS rules.

tr.shown, tr.hidden {
  display: table-row;
}
tr.hidden {
  display: none;
}
.row button {
  background-color: transparent;
  border: .1em solid transparent;
  font: inherit;
  padding: 0.25em 0.5em 0.25em .25em;
  width: 100%;
  text-align: left;
}
.row button:focus, .row button:hover {
  background-color: #ddd;
  outline: .2em solid #00f;
}
.row button svg {
  width: .8em;
  height: .8em;
  margin: 0 0 -.05em 0;
  fill: #66f;
  transition: transform 0.25s ease-in;
  transform-origin: center 45%;
}
.row button:hover svg,
.row button:focus svg {
  fill: #00c;
}
/* Lean on programmatic state for styling */
.row button[aria-expanded="true"] svg {
  transform: rotate(180deg);
}
.cell button {
  font-size: 60%;
  color: #000;
  background-color: #00f;
  padding: 0.3em 0.2em 0 0.2em;
  border: 0.2em solid #00f;
  border-radius: 50%;
  line-height: 1;
  text-align: center;
  text-indent: 0;
  transform: rotate(270deg);
}
.cell button svg {
  width: 1.25em;
  height: 1.25em;
  fill: #fff;
  transition: transform 0.25s ease-in;
  transform-origin: center 45%;
}
.cell button:hover,
.cell button:focus {
  background-color: #fff;
  outline: none;
}
.cell button:hover svg,
.cell button:focus svg {
  fill: #00f;
}
/* Lean on programmatic state for styling */
.cell button[aria-expanded="true"] svg {
  transform: rotate(90deg);
}
/* Proven method to visually hide something but */
/* still make it available to assistive technology */
.visually-hidden {
  position: absolute;
  top: auto;
  overflow: hidden;
  clip: rect(1px 1px 1px 1px); /* IE 6/7 */
  clip: rect(1px, 1px, 1px, 1px);
  width: 1px;
  height: 1px;
  white-space: nowrap;
}

The main function to expand/collapse the table rows when you click on the toggle button.

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");
  }
}