padLeft - Function for padding strings on the left side

padLeft.js

/**
 * Pads `string` on the left side if it's shorter than `length`. Padding
 * characters are truncated if they exceed `length`.
 *
 * @param {string} [string=''] The string to pad.
 * @param {number} [length=0] The padding length.
 * @param {string} [chars='0'] The string used as padding.
 * @returns {string} Returns the padded string.
 * @example
 *
 * padLeft('123', 6);
 * // => '000123'
 *
 * padLeft('123', 6, '-');
 * // => '---123'
 *
 * padLeft('123', 3);
 * // => '123'
  *
 * padLeft('1234', 3);
 * // => '1234'
 */
function padLeft(string, length, chars) {
  string = string == null ? '' : string;
  length = length ? length : 0;
  chars = chars ? chars : ' ';

  var max = (length - string.length)/chars.length,
      i;

  for (i = 0; i < max; i++) {
    string = chars + string;
  }

  return string;
}