//1. 经典洗牌算法实现

function shuffle(array) {

let arrayLength = array.length,

randomIndex, //随机数

tempItem; //临时存储元素

for (let i = arrayLength - 1; i >= 0; i--) {

randomIndex = Math.floor(Math.random() * (i + 1));

tempItem = array[randomIndex];

array[randomIndex] = array[i];

array[i] = tempItem;

}

return array;