Zero Padding in JavaScript

zero-padding.js

function zeroPadding(number, length) {
  return (Array(length).join('0') + number).slice(-length);
}

zeroPadding(240, 10) // 0000000240


/**
 * String.prototype.padStart()
 * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/padStart
 */
const str = 'abc';

str.padStart(10);         // "       abc"
str.padStart(10, "foo");  // "foofoofabc"
str.padStart(6,"123465"); // "123abc"
str.padStart(8, "0");     // "00000abc"
str.padStart(1);          // "abc"