JavaScript padding tolerant to ANSI escape sequences

padding.js

/**
 * Display a string with padding
 *
 * @param {String}  str String to pad
 * @param {Integer} l   padding length
 * @param {Boolean} [r] true for right padding
 *
 * @return {String}
 */
function pad(str, l, r) {
  "use strict";
  var tmp = new Array(l).join(' ');
  str = '' + str;
  var strClean = str.replace(/\u001b\[[^m]+m/g, '');

  return r ? tmp.substr(0, l - strClean.length) + str.substr(0, l + str.length - strClean.length) : str.substr(0, l + str.length - strClean.length) + tmp.substr(0, l - strClean.length);
}