Format a Number, Exactly Two in Length?

Question

I have an integer that is less then 100 and is printed to an HTML page with JavaScript. How do I format the integer so that it is exactly two digits long? For example:

Answer 1

Improved version of previous answer:

var result = [...Array(12)].map((_, i) => zeroFill(i + 1, 2));

function zeroFill(num, size) {
  let s = num + '';
  while (s.length < size) s = `0${s}`;
  return s;
}
console.log(result)