var a = [1, 2, 3, 4, 5];

// function randomSort1(a, b) {
//   return Math.random() > 0.5 ? -1 : 1;
// }

function randomSort(arr) {
  for (let i = 0, len = arr.length; i < len; i++) {
    let random = Math.floor(Math.random() * len);
    let cur = arr[i];
    arr[i] = arr[random];
    arr[random] = cur;
  }
}
randomSort(a);
console.log(a);