Fisher-Yates乱序

1.实现

function shuffle(arr) {
    let j,x,i
  for(i = arr.length;i;i--) {
      j = Math.floor(Math.random()*i)
    x = arr[i-1]
    arr[i-1] = arr[j]
    arr[j] = x
  }
  return arr
}