JS-CSS: Remove Outline on Focus (accessible)

no-focus-outline.css

html:not(.no-js):not(.user-is-tabbing) button:focus,
html:not(.no-js):not(.user-is-tabbing) input:focus,
html:not(.no-js):not(.user-is-tabbing) select:focus,
html:not(.no-js):not(.user-is-tabbing) textarea:focus {
  outline: none;
}

no-focus-outline.js

var addUserTabbingClass = function( event ) {
    if ( event.keyCode === 9 ) { // tab key
        document.documentElement.classList.add( 'user-is-tabbing' );
        window.removeEventListener( 'keydown', addUserTabbingClass );
    }
}

window.addEventListener( 'keydown', addUserTabbingClass );