javascript數組排列組合和洗牌算法Fisher–Yates shuffle

//數組亂序    洗牌算法Fisher–Yates shuffle
Array.prototype.shuffle = function() {
    var input = this;
    for (var i = input.length-1; i >=0; i--) {
        var randomIndex = Math.floor(Math.random()*(i+1));
        var itemAtIndex = input[randomIndex];
        input[randomIndex] = input[i];
        input[i] = itemAtIndex;
    }
    return input;
}
//數組排列組合
Array.prototype.permute = function() {
    var permArr = [],
        usedChars = [];
    var input = this;
    function main(input){
        var i, ch;
        for (i = 0; i < input.length; i++) {
            ch = input.splice(i, 1)[0];
            usedChars.push(ch);
            if (input.length == 0) {
                permArr.push(usedChars.slice());
            }
            main(input);
            input.splice(i, 0, ch);
            usedChars.pop();
        }
        return permArr
    }
    return main(input);
}