数组乱排

function shuffle(arr) {
  let array = arr;
  let index = array.length;

  while (index) {
    index -= 1;
    let randomInedx = Math.floor(Math.random() * index);
    let middleware = array[index];
    array[index] = array[randomInedx];
    array[randomInedx] = middleware;
  }

  return array;
}