Javascript Array.shuffleAndClip()

Array.shuffleAndClip()

Array.prototype.shuffleAndClip = function (len) {
    var array = this;
    if(len && array.length && len > array.length - 1) {
        len = null;
    }
    for(var rnd, value, i = array.length; i;
        rnd = Math.floor(Math.random() * i),
        value = array[--i],
        array[i] = array[rnd],
        array[rnd] = value);
    return len ? array.slice(0, len) : array;
}