How to output numbers with leading zeros in JavaScript? [duplicate]

UPDATE: Small one-liner function using the ES2017 String.prototype.padStart method:

const zeroPad = (num, places) => String(num).padStart(places, '0')

console.log(zeroPad(5, 2)); // "05"
console.log(zeroPad(5, 4)); // "0005"
console.log(zeroPad(5, 6)); // "000005"
console.log(zeroPad(1234, 2)); // "1234"

Another ES5 approach:

function zeroPad(num, places) {
  var zero = places - num.toString().length + 1;
  return Array(+(zero > 0 && zero)).join("0") + num;
}

zeroPad(5, 2); // "05"
zeroPad(5, 4); // "0005"
zeroPad(5, 6); // "000005"
zeroPad(1234, 2); // "1234" :)

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