function str_pad (input, pad_length, pad_string, pad_type) {
  // http://kevin.vanzonneveld.net
  // +   original by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // + namespaced by: Michael White (http://getsprink.com)
  // +      input by: Marco van Oort
  // +   bugfixed by: Brett Zamir (http://brett-zamir.me)
  // *     example 1: str_pad('Kevin van Zonneveld', 30, '-=', 'STR_PAD_LEFT');
  // *     returns 1: '-=-=-=-=-=-Kevin van Zonneveld'
  // *     example 2: str_pad('Kevin van Zonneveld', 30, '-', 'STR_PAD_BOTH');
  // *     returns 2: '------Kevin van Zonneveld-----'
  var half = '',
    pad_to_go;

  var str_pad_repeater = function (s, len) {
    var collect = '',
      i;

    while (collect.length < len) {
      collect += s;
    }
    collect = collect.substr(0, len);

    return collect;
  };

  input += '';
  pad_string = pad_string !== undefined ? pad_string : ' ';

  if (pad_type !== 'STR_PAD_LEFT' && pad_type !== 'STR_PAD_RIGHT' && pad_type !== 'STR_PAD_BOTH') {
    pad_type = 'STR_PAD_RIGHT';
  }
  if ((pad_to_go = pad_length - input.length) > 0) {
    if (pad_type === 'STR_PAD_LEFT') {
      input = str_pad_repeater(pad_string, pad_to_go) + input;
    } else if (pad_type === 'STR_PAD_RIGHT') {
      input = input + str_pad_repeater(pad_string, pad_to_go);
    } else if (pad_type === 'STR_PAD_BOTH') {
      half = str_pad_repeater(pad_string, Math.ceil(pad_to_go / 2));
      input = half + input + half;
      input = input.substr(0, pad_length);
    }
  }

  return input;
}

str_pad('Kevin van Zonneveld', 30, '-=', 'STR_PAD_LEFT');

'-=-=-=-=-=-Kevin van Zonneveld'

str_pad('Kevin van Zonneveld', 30, '-', 'STR_PAD_BOTH');

'------Kevin van Zonneveld-----'