Equals method in Javascript

gistfile1.txt

String.prototype.equals = function(s) {
  if(typeof(s) == "object") {
    return this.valueOf() === s.valueOf();
  }
  else if(typeof(s) == "string") {
    return this.valueOf() === s;
  }
  else {
		return undefined;
	}
};

console.log("123".equals("123"));
console.log("123".equals(new String("123")));