UUID v4 JavaScript implementation with window.crypto.getRandomValues()

uuid.js

function uuid () {
    function getRandomSymbol (symbol) {
        var array;

        if (symbol === 'y') {
            array = ['8', '9', 'a', 'b'];
            return array[Math.floor(Math.random() * array.length)];
        }

        array = new Uint8Array(1);
        window.crypto.getRandomValues(array);
        return (array[0] % 16).toString(16);
    }
    
    return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, getRandomSymbol);
}