Weird bug in Javascript splice method

Question

I have an array which contains "Zeros" and I want to move all of the "Zeros" to the last indexes of the array.

The expected output is:

[1,2,3,0,0,0,0]

But instead I get:

[1,2,0,3,0,0,0]

let a = [0, 1, 2, 0, 0, 3, 0];
let count = 0;
let len = a.length;

for (i = 0; i < len; i++) {
  if (a[i] == 0) {
    count = count + 1;
    a.splice(i, 1);
  }
}

for (j = 0; j < count; j++) {
  a.push(0);
}

console.log(a);

Answer 1

When you remove the item from the array all the element shift down by one. When you advance your index (i++), you skip the shifted down item in the array which happens to be successive zero in the array.

Solution: Do the for next loop backward and it'll work.