Javascript String empty()

// alias of isEmpty
String.prototype.empty = function() {
  return this == '';
};

String.prototype.empty = function() {
  return this.length == 0;
}

String.prototype.empty = function empty () {
  return this.clean() === '';
};

String.prototype.empty = function() {
    return ( this == "" || this.length == 0 ) ?true:false;
}