The element is deleted, but the original address is still retained, so the subsequent elements must be moved forward. This will reduce the number of elements and update the length

Will be updated

var tt = [1, 2, 3]; tt.length // 3 tt.splice(0, 1); // [1] tt.length //2

For your needs, you can write a method yourself and encapsulate splice:

function my_splice(arr, start, length) { arr.splice(start, length); return arr.length; }