How can I format an integer to a specific length in javascript?

Question

I have a number in Javascript, that I know is less than 10000 and also non-negative. I want to display it as a four-digit number, with leading zeroes. Is there anything more e

Answer 1

Latest with ES6 repeat() method:

    const length_required = 5;
    let num = 10;
    num = "0".repeat(length_required - String(num).length) + num;
    console.log(num)
    // output: 00010

    let num = 1000;
    num = "0".repeat(length_required - String(num).length) + num;
    console.log(num)
    // output: 01000