understrap/src/js/skip-link-focus-fix.js

46 lines
906 B
JavaScript

/**
* File skip-link-focus-fix.js.
*
* Helps with accessibility for keyboard only users.
*
* Learn more: https://git.io/vWdr2
*/
( () => {
const isWebkit = navigator.userAgent.toLowerCase().indexOf( 'webkit' ) > -1,
isOpera = navigator.userAgent.toLowerCase().indexOf( 'opera' ) > -1,
isIe = navigator.userAgent.toLowerCase().indexOf( 'msie' ) > -1;
if (
( isWebkit || isOpera || isIe ) &&
document.getElementById &&
window.addEventListener
) {
window.addEventListener(
'hashchange',
() => {
let id = location.hash.substring( 1 ),
element;
if ( ! /^[A-z0-9_-]+$/.test( id ) ) {
return;
}
element = document.getElementById( id );
if ( element ) {
if (
! /^(?:a|select|input|button|textarea)$/i.test(
element.tagName
)
) {
element.tabIndex = -1;
}
element.focus();
}
},
false
);
}
} )();