answer1.js

function moveAllZerosToLeft(input) {
  let zeros = [];
  let numbers = [];
  for (const element of input) {
    if (element === 0) {
      zeros.push(element);
    } else {
      numbers.push(element);
    }
  }
  return zeros.concat(numbers);
}

answer2.js

function moveAllZerosToLeft(input) {
  let result = [];
  for (const element of input) {
    if (element === 0) {
      result.push(element);
    }
  }
  for (const element of input) {
    if (element !== 0) {
      result.push(element);
    }
  }
  return result;
}

answer3.js

function moveAllZerosToLeft(input) {
  for (let idx = 0; idx < input.length; ++idx) {
    if (input[idx] !== 0) {
      continue;
    }
    input.unshift(input.splice(idx, 1)[0]);
  }
  return input;
}