ARIA: tab role - Accessibility 编辑

The ARIA tab role indicates an interactive element inside a tablist that, when activated, displays its associated tabpanel.

<button role="tab" aria-selected="true" aria-controls="tabpanel-id" id="tab-id">Tab label</button>

Description

An element with the tab role controls the visibility of an associated element with the tabpanel role. The common user experience pattern is a group of visual tabs above, or to the side of, a content area, and selecting a different tab changes the content and makes the selected tab more prominent than the other tabs.

Elements with the role tab must either be a child of an element with the tablist role, or have their id part of the aria-owns property of a tablist. This combination identifies to assistive technology that the element is part of a group of related elements. Some assistive technology will provide a count of the number of tab role elements inside a tablist, and inform users of which tab they currently have targeted. They should contain the aria-controls property identifying an element with the tabpanel role. When an element with the tabpanel role has focus, or a child of it has focus, that indicates that the connected element with the tab role is the active tab in a tablist.

When working with elements with the tab role, when they are selected or active, they should have their aria-selected attribute set to true, otherwise it should be set to false. When a tab is selected or active, its controlled tabpanel should have its aria-expanded attribute set to true and its hidden attribute set to false, otherwise the reverse.

Associated Roles and Attributes

aria-selected

boolean

aria-controls

id of element with tabpanel role

id

content

Keyboard interaction

Required JavaScript features 

While there are ways to build tab-like functionality without JavaScript, there are no substitute combination of HTML and CSS only that will provide the same set of functionality that's required above for accessible tabs with content.

Example

This example combines the role tab with tablist and elements with tabpanel to create an interactive group of tabbed content. Here we are enclosing our group of content in a div, with our tablist having an aria-label to label it for assistive technology. Each tab is a button with the attributes previously mentioned. The first tab has tabindex=0 on it, which we will later change to whatever tab has aria-selected=true. All of the tabpanel elements have tabindex=0 to make them tabbable, and all but the currently active one have the hidden attribute, which we will change with JavaScript. There is some basic styling applied that restyles the buttons and changes the z-index to of tab elements to give the illusion of it connecting to the tabpanel for active elements, and the illusion that inactive elements are behind the active tabpanel.

<div class="tabs">
  <div role="tablist" aria-label="Sample Tabs">
    <button role="tab" aria-selected="true" aria-controls="panel-1" id="tab-1" tabindex="0">
          First Tab
        </button>
    <button role="tab" aria-selected="false" aria-controls="panel-2" id="tab-2" tabindex="-1">
          Second Tab
        </button>
    <button role="tab" aria-selected="false" aria-controls="panel-3" id="tab-3" tabindex="-1">
          Third Tab
        </button>
  </div>
  <div id="panel-1" role="tabpanel" tabindex="0" aria-labelledby="tab-1">
    <p>Content for the first panel</p>
  </div>
  <div id="panel-2" role="tabpanel" tabindex="0" aria-labelledby="tab-2" hidden>
    <p>Content for the second panel</p>
  </div>
  <div id="panel-3" role="tabpanel" tabindex="0" aria-labelledby="tab-3" hidden>
    <p>Content for the third panel</p>
  </div>
</div>

.tabs {
  padding: 1em;
}

[role="tablist"] {
  margin-bottom: -1px;
}

[role="tab"] {
  position: relative;
  z-index: 1;
  background: white;
  border-radius: 5px 5px 0 0;
  border: 1px solid grey;
  border-bottom: 0;
  padding: 0.2em;
}

[role="tab"][aria-selected="true"] {
  z-index: 3;
}

[role="tabpanel"] {
  position: relative;
  padding: 0 0.5em 0.5em 0.7em;
  border: 1px solid grey;
  border-radius: 0 0 5px 5px;
  background: white;
  z-index: 2;
}

[role="tabpanel"]:focus {
  border-color: orange;
  outline: 1px solid orange;
}

There are two things we need to do with JavaScript: we need to change focus and tab index of our tab elements with the right and left arrows, and we need to change the active tab and tabpanel when we click on a tab.

To accomplish the first, we listen for the keydown event on the tablist. If the event's keyCode is 39 for right arrow or 37 for the left arrow, we react to the event. We start by setting the tabindex of the current tab element to -1, making it no longer tabbable. Then, if the right arrow is being pressed, we increase our tab focus counter by one. If the counter is greater than the number of tab elements we have, we circle back to the first tab by setting that counter to 0. If the left arrow is being pressed, we decrease our tab focus counter by one, and if it is then less than 0, we set it number of tab elements minus one (to get to the last element). Finally, we set focus to the tab element whose index is equal to the tab focus counter, and set its tabindex to 0 to make it tabbable.

To handle changing the active tab and tabpanel, we have a function that takes in the event, gets the element that triggered the event, the triggering element's parent element, and its grandparent element. We then find all tabs with aria-selected=true inside the parent element and sets it to false, then sets the triggering element's aria-selected to true. After that, we find all tabpanel elements in the grandparent element, make them all hidden, and finally select the element whose id is equal to the triggering tab's aria-controls and removes the hidden attribute, making it visible.

window.addEventListener("DOMContentLoaded", () => {
  const tabs = document.querySelectorAll('[role="tab"]');
  const tabList = document.querySelector('[role="tablist"]');

  // Add a click event handler to each tab
  tabs.forEach(tab => {
    tab.addEventListener("click", changeTabs);
  });

  // Enable arrow navigation between tabs in the tab list
  let tabFocus = 0;

  tabList.addEventListener("keydown", e => {
    // Move right
    if (e.keyCode === 39 || e.keyCode === 37) {
      tabs[tabFocus].setAttribute("tabindex", -1);
      if (e.keyCode === 39) {
        tabFocus++;
        // If we're at the end, go to the start
        if (tabFocus >= tabs.length) {
          tabFocus = 0;
        }
        // Move left
      } else if (e.keyCode === 37) {
        tabFocus--;
        // If we're at the start, move to the end
        if (tabFocus < 0) {
          tabFocus = tabs.length - 1;
        }
      }

      tabs[tabFocus].setAttribute("tabindex", 0);
      tabs[tabFocus].focus();
    }
  });
});

function changeTabs(e) {
  const target = e.target;
  const parent = target.parentNode;
  const grandparent = parent.parentNode;

  // Remove all current selected tabs
  parent
    .querySelectorAll('[aria-selected="true"]')
    .forEach(t => t.setAttribute("aria-selected", false));

  // Set this tab as selected
  target.setAttribute("aria-selected", true);

  // Hide all tab panels
  grandparent
    .querySelectorAll('[role="tabpanel"]')
    .forEach(p => p.setAttribute("hidden", true));

  // Show the selected panel
  grandparent.parentNode
    .querySelector(`#${target.getAttribute("aria-controls")}`)
    .removeAttribute("hidden");
}

Best practices

It is recommended to use a button element with the role tab for their built-in functional and accessible features instead, as opposed to needing to add them yourself. For controlling tab key functionality for elements with the role tab, it is recommended to set all non-active elements to tabindex=-1, and to set the active element to tabindex=0.

Specifications

Precedence order

What are the related properties, and in what order will this attribute or property be read (which property will take precedence over this one, and which property will be overwritten.

Screen reader support

TBD