数组反转

答案

对撞指针

1. 声明两个对撞指针 left/right
2. while 循环条件 left < right
3. 数组两两交换：[arr[left],arr[right]] = [arr[right],arr[left]]

function reverse(arr){
  let left = 0
  let right = arr.length -1

  while(left < right){
    [arr[left],arr[right]] = [arr[right],arr[left]]

    left ++
    right --
  }
  return arr
}

var arr = [1,2,3,4,5]
console.log(reverse(arr))

// [5,4,3,2,1]