假如有一个数组是这样子：
var arr1 = ["a", "b", "c", "d"];
如何随机打乱数组顺序，也即洗牌。
有一个比较广为传播的简单随机算法：
function RandomSort (a,b){ return (0.5 - Math.random()); }实际证明上面这个并不完全随机。
随便一搜网上太多这种东西了，看一下stackoverflow上的一个高分回答，答案出自github上。
knuth-shuffle
The Fisher-Yates (aka Knuth) shuffle for Browser and Node.JS
下面一起看看上面说的这个算法，代码如下：
/*jshint -W054 */(function (exports) {'use strict';// http://stackoverflow.com/questions/2450954/how-to-randomize-shuffle-a-javascript-arrayfunction shuffle(array) {var currentIndex = array.length, temporaryValue, randomIndex;// While there remain elements to shuffle...while (0 !== currentIndex) {// Pick a remaining element...randomIndex = Math.floor(Math.random() * currentIndex);currentIndex -= 1;// And swap it with the current element.temporaryValue = array[currentIndex];array[currentIndex] = array[randomIndex];array[randomIndex] = temporaryValue;}return array;}exports.knuthShuffle = shuffle;}('undefined' !== typeof exports && exports || 'undefined' !== typeof window && window || global));作者推荐使用浏览器写法：
(function () {'use strict';var a = [2,11,37,42], b;// The shuffle modifies the original array// calling a.slice(0) creates a copy, which is assigned to bb = window.knuthShuffle(a.slice(0));console.log(b);}());Nodejs：
npm install -S knuth-shuffle(function () {'use strict';var shuffle = require('knuth-shuffle').knuthShuffle, a = [2,11,37,42], b;// The shuffle modifies the original array// calling a.slice(0) creates a copy, which is assigned to bb = shuffle(a.slice(0));console.log(b);}());还有其它从这个算法中变形去的，比如下面这个for循环的。其它的就不说了。
/*** Randomize array element order in-place.* Using Durstenfeld shuffle algorithm.*/function shuffleArray(array) {for (var i = array.length - 1; i > 0; i--) {var j = Math.floor(Math.random() * (i + 1));var temp = array[i];array[i] = array[j];array[j] = temp;}return array;}使用ES2015（ES6）
Array.prototype.shuffle = function() {let m = this.length, i;while (m) {i = (Math.random() * m--) >>> 0;[this[m], this[i]] = [this[i], this[m]]}return this;}使用：
[1, 2, 3, 4, 5, 6, 7].shuffle();
发现中文搜索随机算法一大堆，但究竟是不是完全随机，效率和兼容性都有待考究，建议后面如果有需要用到随机打乱数组元素，可以用上面这个。