Javascript String toLowerCase() method

String.prototype.toLowerCase = function() {
  var s = "";
  for (var i = 0, len = this.length; i < len; i++) {
    var char = this.charCodeAt(i);
    if (char >= 65 && char <= 90) {
      s += String.fromCharCode(char + 32);
    } else {/*from  ww  w . ja  va2  s . com*/
      s += this[i];
    }
  }
  
  return s;
};