js将一个数组彻底打乱排序

方法一： 

let x = [1, 2, 3, 4, 5];
function shuffle(arr) {
  var length = arr.length,
    randomIndex,
    temp;
  while (length) {
    randomIndex = Math.floor(Math.random() * (length--));
    temp = arr[randomIndex];
    arr[randomIndex] = arr[length];
    arr[length] = temp
  }
  return arr;
}
console.log(shuffle(x))

结果：

[5, 3, 2, 1, 4]

方法二： 

var a = [1,4,2,4,3,6]
const shuffle = (arr) => {
  for (let i = 0; i < arr.length; i++) {
    const randomIndex = Math.round(Math.random() * (arr.length - 1 - i)) + i;
    [arr[i], arr[randomIndex]] = [arr[randomIndex], arr[i]]
  }
  return arr
};

console.log(shuffle(a))

结果：[2, 6, 4, 3, 4, 1]

方法三：

var a = [1, 2, 3, 4, 5];
a.sort(randomSort);
console.log(a);
function randomSort(a, b) { return Math.random() > 0.5 ? -1 : 1; }

结果：[5, 3, 2, 1, 4]