owncast/build/javascript/node_modules/tabbable

tabbable

Returns an array of all* tabbable DOM nodes within a containing node. (* "all" has some necessary caveats, which you'll learn about by reading below.)

The following are considered tabbable:

• <button>s
• <input>s
• <select>s
• <textarea>s
• <a>s with href or xlink:href attributes
• <audio>s and <videos>s with controls attributes
• [contenteditable] elements
• anything with a non-negative tabindex

Any of the above will not be considered tabbable, though, if any of the following are also true about it:

• negative tabindex
• disabled
• either the node itself or an ancestor of it is hidden via display: none or visibility: hidden
• it's an <input type="radio"> and a different radio in its group is checked

If you think a node should be included in your array of tabbables but it's not, all you need to do is add tabindex="0" to deliberately include it. (Or if it is in your array but you don't want it, you can add tabindex="-1" to deliberately exclude it.) This will also result in more consistent cross-browser behavior. For information about why your special node might not be included, see "More details", below.

Goals

• Accurate (or, as accurate as possible & reasonable)
• No dependencies
• Small
• Fast

Browser Support

Basically IE9+.

Why? It uses Element.querySelectorAll() and Window.getComputedStyle().

Installation

npm install tabbable

Dependencies: none.

You'll need to be compiling CommonJS (via browserify or webpack).

API

tabbable

tabbable(rootNode, [options])

Returns an array of ordered tabbable node within the rootNode.

Summary of ordering principles:

• First include any nodes with positive tabindex attributes (1 or higher), ordered by ascending tabindex and source order.
• Then include any nodes with a zero tabindex and any element that by default receives focus (listed above) and does not have a positive tabindex set, in source order.

rootNode

Type: Node. Required.

options

includeContainer

Type: boolean. Default: false.

If set to true, rootNode will be included in the returned tabbable node array, if rootNode is tabbable.

tabbable.isTabbable

tabbable.isTabbable(node)

Returns a boolean indicating whether the provided node is considered tabbable.

tabbable.isFocusable

tabbable.isFocusable(node)

Returns a boolean indicating whether the provided node is considered focusable.

All tabbable elements are focusable, but not all focusable elements are tabbable. For example, elements with tabindex="-1" are focusable but not tabbable.

More details

• Tabbable tries to identify elements that are reliably tabbable across (not dead) browsers. Browsers are stupidly inconsistent in their behavior, though — especially for edge-case elements like <object> and <iframe> — so this means some elements that you can tab to in some browsers will be left out of the results. (To learn more about that stupid inconsistency, see this amazing table). To provide better consistency across browsers and ensure the elements you want in your tabbables list show up there, try adding tabindex="0" to edge-case elements that Tabbable ignores.
• (Exemplifying the above ^^:) The tabbability of <iframe>s, <embed>s, <object>s, <summary>s, and <svg>s is inconsistent across browsers, so if you need an accurate read on one of these elements you should try giving it a tabindex. (You'll also need to pay attention to the focusable attribute on SVGs in IE & Edge.) But you also might not be able to get an accurate read — so you should avoid relying on it.
• Radio groups have some edge cases, which you can avoid by always having a checked one in each group (and that is what you should usually do anyway). If there is no checked radio in the radio group, all of the radios will be considered tabbable. (Some browsers do this, otherwise don't — there's not consistency.)
• If you're thinking, "Why not just use the right querySelectorAll?", you may be on to something ... but, as with most "just" statements, you're probably not. For example, a simple querySelectorAll approach will not figure out whether an element is hidden, and therefore not actually tabbable. (That said, if you do think Tabbable can be simplified or otherwise improved, I'd love to hear your idea.)
• jQuery UI's :tabbable selector ignores elements with height and width of 0. I'm not sure why — because I've found that I can still tab to those elements. So I kept them in. Only elements hidden with display: none or visibility: hidden are left out.
• Although Tabbable tries to deal with positive tabindexes, you should not use positive tabindexes. Accessibility experts seem to be in (rare) unanimous and clear consent about this: rely on the order of elements in the document.
• Safari on Mac OS X does not Tab to <a> elements by default: you have to change a setting to get the standard behavior. Tabbable does not know whether you've changed that setting or not, so it will include <a> elements in its list.

Feedback and contributions more than welcome!