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// https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/keyCode#non-printable_keys_function_keys
const keyboardNavigationKeycodes = [ 9, 32, 37, 38, 39, 40 ]; // keyCodes for tab, space, left, up, right, down respectively
// https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/key/Key_Values
const keyboardNavigationKeyValues = [
'Tab',
' ',
// Some browsers returned `'Spacebar'` rather than `' '` for the Space key
'Spacebar',
'ArrowDown',
'ArrowUp',
'ArrowLeft',
'ArrowRight',
];
declare global {
interface KeyboardEvent {
/**
* https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/keyIdentifier
* Provides Safari support
* @deprecated
*/
keyIdentifier: string;
}
}
/**
* `event.keyCode` is [deprecated](https://stackoverflow.com/a/35395154), so we must check each of the following:
* 1. `event.key`
* 2. `event.keyIdentifier`
* 3. `event.keyCode` (for posterity)
*
* However, [`event.key`](https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/key)
* and [`event.keyIdentifier`](https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/keyIdentifier)
* both return a string rather than a numerical key code as the old `keyCode` API did.
*
* Therefore, we have two arrays of keycodes, one for the string APIs and one for the
* older number based API.
* @param event The keyboard event to detect keyboard navigation against.
*/
export function detectKeyboardNavigation( event: KeyboardEvent ): boolean {
let code: number | string | undefined;
if ( event.key !== undefined ) {
code = event.key;
} else if ( event.keyIdentifier !== undefined ) {
code = event.keyIdentifier;
} else if ( event.keyCode !== undefined ) {
code = event.keyCode;
}
// This shouldn't ever happen but we do it to appease TypeScript
if ( code === undefined ) {
return false;
}
if ( typeof code === 'string' ) {
return keyboardNavigationKeyValues.indexOf( code ) !== -1;
}
return keyboardNavigationKeycodes.indexOf( code ) !== -1;
}
let keyboardNavigation = false;
export default function accessibleFocus(): void {
document.addEventListener( 'keydown', function ( event ) {
if ( keyboardNavigation ) {
return;
}
if ( detectKeyboardNavigation( event ) ) {
keyboardNavigation = true;
document.documentElement.classList.add( 'accessible-focus' );
}
} );
document.addEventListener( 'mouseup', function () {
if ( ! keyboardNavigation ) {
return;
}
keyboardNavigation = false;
document.documentElement.classList.remove( 'accessible-focus' );
} );
}
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