@accede-web/overlay

AcceDe Web - overlay

WAI-ARIA overlay plugin without dependencies.

This plugin is written in ES2015 and available either in uncompiled form in the /lib folder or compiled for ES5 in the /dist folder. If your project uses babel with Webpack or Rollup, you should change the exclusion so this plugin gets compiled or force Webpack or Rollup to fetch the compiled version by using the main entry of the package.json file instead of the module entry.

// .babelrc file or configuration within webpack or rollup
{
  "plugins": [...],
  "exclude": "node_modules/!(@accede-web)/**",
}

Installation

$ npm install @accede-web/overlay

Methods

Name	Description
show()	Switch the aria-hidden attribute to false and disable the rest of the document (if the modal parameter is not set to false)
close( returnValue )	Switch the aria-hidden attribute to true and enable the rest of the document if needed. Dispatch close event on the overlay. Also available on the root element of the overlay. The returnValue property can be sent invoking this method
reset()	After passing a formatted overlay to the constructor, the .reset() method can be called when the overlay is closed to put back the element to it's original place
addEventListener(eventName, callback)	Shortcut to listen to the close or cancel events
removeEventListener(eventName, callback)	Shortcut to stop listening to the close or cancel events

Properties

Name	Description
el	The HTML root element of the overlay
returnValue	Also available on the HTML root element. Allows you to pass data between the overlay and the document

Static properties

Contrary to the instance's properties, the static properties are available on the constructor.

Name	Description
stack	Pending overlay stack. Array of all the overlays currently open

Events

Name	Description
close	Triggered when the method .close() is called
cancel	Triggered when the parameter closeOnCancel is true and an escape key keydown or a click outside the overlay is happening. Can be prevented with event.preventDefault(). Triggers a close event when not prevented

Inserting an element in an overlay

HTML

<!-- content to be inserted in an overlay -->
<section class="overlay">
  <header class="layer-header">
    <button class="button-close">
      <span>Close</span>
    </button>
    <h2 class="layer-title">Modal window</h2>
  </header>
  <div class="layer-content">
    <p>…</p>
  </div>
</section>

JavaScript

// the content property can be an HTMLElement
var overlay = new Overlay({
  content: document.querySelector( '.overlay' )
});

// … or an HTML string
var overlay = new Overlay({
  content: '<div><p>Hello</p></div>'
});

overlay.addEventListener( 'close', e => {
  // the value returned by the overlay
  console.log( e.target.returnValue );
});

// Display the overlay
overlay.show();

// Close the overlay and pass the return value
overlay.close( 'returnValueData' );

Parameters

Mandatory parameters

Name	Type	Description
content	HTMLElement or String	Content to insert in the overlay.

Optional parameters

Name	Type	Description
className	String	HTML classes to add to the overlay (space separated)
closeOnCancel	Boolean	Allow the Escape key or a click outside the overlay to close it. Defaults to true
closeSelector	String	CSS selector to match any element that will close the overlay when clicked
modal	Boolean	Should the overlay be modal (disable anything but the overlay on the page). Defaults to true
opener	HTMLElement	HTML element that will receive the focus once the overlay is closed. Defaults to the current active element
tagName	String	Change the tag name of the overlay. Defaults to <div>
role	String	Specify the role attribute of the overlay. Can be dialog or alertdialog
titleSelector	String	Mandatory when using a role attribute and no label property, a CSS selector matching the title the overlay should have. Defaults to [data-label]
label	String	Mandatory when using a role attribute and there's no title displayed in the overlay to specify the title of the overlay

Passing the formatted element

In this case the overlay is a valid and accessible HTML structure passed to the script. The script is used to handle the events and to disable the document.

HTML

<!-- valid overlay structure example -->
<div role="alertdialog" class="layer" aria-hidden="true" aria-labelledby="layerTitle" aria-describedby="layerDesc">
  <section class="layer">
    <header class="layer-header">
      <button class="button-close">
        <span>Close</span>
      </button>
      <h2 class="layer-title" id="layerTitle">Warning</h2>
    </header>
    <div class="layer-content">
      <p id="layerDesc">Your confirmation number is required before continuing.</p>
    </div>
  </section>
</div>

JavaScript

var overlay = new Overlay( document.querySelector( '.layer' ), {
  closeOnCancel: false,
  opener: document.querySelector( 'button' ),
  closeSelector, '.button-close'
  modal: false
});

// Display the overlay
overlay.show();

// Close the overlay
overlay.close();

Optional parameters

Name	Type	Description
closeOnCancel	Boolean	Allow the Escape key or a click outside the overlay to close it. Defaults to true
closeSelector	String	CSS selector to match any element that will close the overlay when clicked
modal	Boolean	Should the overlay be modal (disable anything but the overlay on the page). Defaults to true
opener	HTMLElement	HTML element that will receive the focus once the overlay is closed. Defaults to the current active element

Keyboard Interaction

• Tab: Moves focus to the next tabbable element inside the overlay.
• Shift + Tab: Moves focus to the previous tabbable element inside the overlay.
• Escape: Closes the overlay.

Polyfill

In order to dispatch the close and cancel event, the script uses the CustomEvent constructor. A polyfill for CustomEvent is mandatory when the support of Internet Explorer is required. You can find one on the MDN website.

Compatibilty

This plugin is tested against the following browsers:

• Internet Explorer 11 and higher
• Microsoft Edge
• Chrome
• Firefox
• Safari

Testing

Install the project dependencies:

  $ npm install

Run the automated test cases:

  $ npm test

Development

To test locally, you can run:

  $ npm run server

And then go to http://localhost:3000/test