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agnostic-axe

Developer tool that continously observes the DOM to detect accessibility issues. Its audits are powered by axe-core.

Screenshot of an opened website, with accessibility issues displayed in the browser console

Basic Usage

This is all you need to start reporting accessibility issues to the browser console:

import('https://unpkg.com/agnostic-axe@3').then(
  ({ AxeObserver, logViolations }) => {
    const MyAxeObserver = new AxeObserver(logViolations)
    MyAxeObserver.observe(document)
  }
)

To try agnostic-axe, paste the above code into the browser console on a site of your choosing.

When adding agnostic-axe to your project, be sure to only import it in your development environment. Else your application will use more resources than necessary. (Here's an example of how to do this with webpack)

API Details

AxeObserver constructor

Accepts one parameter:

  • violationsCallback (required). A function that is invoked with an array of violations, as reported by axe-core. To log violations to the console, simply pass the logViolations function exported by this module.

AxeObserver.observe

Accepts one parameter:

  • targetNode (required). A DOM node. AxeObserver audits this node, and continously monitors it for changes. If a change has been detected, AxeObserver audits the parts that have changed, and reports any new accessibility defects.

To observe multiple nodes, one can call the AxeObserver.observe method multiple times.

MyAxeObserver.observe(document.getElementById('react-main'))
MyAxeObserver.observe(document.getElementById('vue-header'))
MyAxeObserver.observe(document.getElementById('page-footer'))

AxeObserver.disconnect

Accepts no parameters.

Invoke this method to stop observing the DOM. This also clears the cache of violations that were already reported.

MyAxeObserver.disconnect()

Interacting with the axe-core API

The instance of axe-core used by agnostic-axe is exported by this module. Import it to interact with the axe-core API.

import('https://unpkg.com/agnostic-axe@3').then(
  ({ axeCoreInstance, AxeObserver, logViolations }) => {
    axeCoreInstance.registerPlugin(myPlugin)
    // ...
  }
)

Comparison with react-axe

Unlike framework specific implementations of axe-core, such as react-axe, agnostic-axe uses a MutationObserver to listen for changes directly in the DOM. This has two advantages:

  1. It works with all web frameworks, and with any of their versions. This is key, as for example, at the time of writing, react-axe does not work with the newer React features (function components and fragments), while agnostic-axe does supports them.
  2. It only runs audits if the actual DOM changes. This means it uses less resources than react-axe, which runs audits when components rerender, even if their output does not change.

agnostic-axe is optimized for performance. Its audits are small chunks of work that run in the browser's idle periods.