aria-api

WAI-ARIA allows websites to provide additional semantics to assistive technologies. Roles and attributes can be set either explicitly (e.g. <span role="link">click me</span>) or implicitly (<a href="//example.com">click me</a> implicitly has the role "link").

While the implicit mappings make authoring accessible websites simpler, it makes the task of calculating an element's role and attributes more complicated. This library takes care of exactly that.

Install

npm install aria-api

This installation method works best if you use tools like webpack or browserify. There is also an UMD build included as dist/aria.js.

Usage

var aria = require('aria-api'):

aria.querySelector('landmark').forEach(landmark => {
    if (!aria.matches(landmark, ':hidden')) {
        var role = aria.getRole(landmark);
        var name = aria.getName(landmark);
        console.log(role, name);
    }
});

getRole(element)

Calculate an element's role.

Note that this will return only the most specific role. If you want to know whether an element has a role, use matches() instead.

getAttribute(element, attribute)

Calculate the value of an element's attribute (state or property). The "aria-" prefix is not included in the attribute name.

getName(element)

Calculate an element's name according to the Accessible Name and Description Computation.

getDescription(element)

Calculate an element's description according to the Accessible Name and Description Computation.

matches(element, selector)

Similar to Element.matches(), this allows to check whether an element matches a selector. A selector can be any of the following:

• role: Matches if the element has the specified role. This also works for hierarchical roles such as "landmark".
• :attribute: Matches if the attribute is truthy. The "aria-" prefix is not included in the attribute name.
• [attribute="value"]: Matches if the value of the attribute converted to string equals the specified value.

Note that combinations of selectors are not supported (e.g. main link, link:hidden, :not(:hidden)). The single exception to this rule are comma-separated lists of roles, e.g. link,button.

querySelector(element, selector)

Similar to Element.querySelector(). See matches() for details.

querySelectorAll(element, selector)

Similar to Element.querySelectorAll(). See matches() for details.

closest(element, selector)

Similar to Element.closest(). See matches() for details.

getParentNode(node)

Similar to Node.parentNode, but takes aria-owns into account.

getChildNodes(node)

Similar to Node.childNodes, but takes aria-owns into account.

What is this for?

First of all, I thought that something like this should exist. I currently use it for a11y-outline, a web extension that generates outlines based on WAI-ARIA roles.

That said, this is what I think it could also be used for:

• Providing features based on the additional information provided by ARIA, e.g. landmark navigation.
• Tools helping developers with improving accessibility.

Implemented standards

• Accessible Rich Internet Applications 1.2
• HTML Accessibility API Mappings 1.0
• SVG Accessibility API Mappings (very incomplete)
• WAI-ARIA Graphics Module 1.0
• Digital Publishing WAI-ARIA Module 1.1
• Accessible Name and Description Computation 1.1

I try to update the code whenever a new version of these specs becomes a recommendation.

Notes

• This is a pet project. I do not have the time to do extensive testing and may skip some details now and then. I am happy to receive bug reports and pull requests though.
• The standards are still in a very rough state. Many things are unclear/undecided and therefore no browser really implements them. So naturally, this library cannot really implement the standards either.
• This library does not do any validity checks. Invalid attributes or roles will not produce any warnings.
• In order to calculate the "hidden" attribute, Window.getComputedStyle() is called. This only seems to return reliable values if the element is attached to document.
• Due to security restrictions it is not generally possible to inspect the content of iframes, so they are ignored.

Related projects

• Visual ARIA Bookmarklet: Displays role, name, and description in any website. Maintained by one of the editors of the accname spec.
• axe-core and Accessibility Developer Tools: These are libraries for accessibility testing. They solve many of the same issues as this library internally.
• ARIA Query: Information from the ARIA spec as JavaScript structures.
• Accessibility Object Model: Draft spec for exposing the accessibility tree to JavaScript.
• chrome.automation: A propriatary API that exposes the accessibility tree to JavaScript.
• babelacc: A tool to compare the output of different libraries.