Accessible modal component with focus trap

Creates a modal container before the </body> tag and optional overlay to act as a portal for the dialog content.

yarn add accessible-modal

API

Create a modal

Instantiate with options

import { AccessibleModal } from 'accessible-modal';

const modal = new AccessibleModal({
  backdropClass: 'overlay',
  closeBtnClass: 'close-button',
});

to create and append a new div with aria attributes to the DOM.

Open the modal

Open using the open() method and pass the HTML to insert into the created modal and toggle its aria-hidden attribute.

modal.open(document.querySelector('.modal'));

Focus management

On opening the modal dialog, focus will be set to the first focusable element in the markup
The focus will be trapped to all focusable elements inside the modal dialog
tab will cycle through the focusable elements; shift+tab will cycle through them in reverse
Upon closing the dialog, the focus will be returned to the last focused item

Closing the modal

If a closeBtnClass is passed in the options, it will be queried for in the HTML element passed on open() and if no such element exists, a button will be created and appended with the appropriate attributes. An event listenter will be attached to provide close functionality.
If no closeBtnClass is passed, no button will be created and no element will have the close() event listener attached.
If backdropClass is passed in the options a backdrop layer will be created which will close the modal on click.
The esc key will close the modal.

Options

backdropClass?: string
If passed, a div is appended before the modal to be used as the overlay, and given this class.

closeBtnClass?: string
The class of the "close modal" button element in the markup that an event listener will be attached to. If not passed, the modal can still be closed by esc.

labelledBy?: string
Creates an aria-labelledby attribute on the modal. This should correspond to the id of an element inside the modal that would make sense as a label for the modal's content.

describedBy?: string
Creates an aria-describedby attribute on the modal. This should correspond to the id of an element inside the modal that would make sense as description text for the modal's content.

Styles

None are provided.

On open(), aria-hidden is set to false on three elements:

The overlay, if used
The modal created on instantiation
The HTML element passed to the open() method

therefore [aria-hidden="true"] { display: none; } is convenient CSS to hide the backdrop layer as well as the modal if it is pre-rendered in the markup.