String.prototype.myComment; String.prototype.getLength = function(){ return this.length; } String.prototype.toString = function(){ return "김덕배님의 말 : " + this.valueOf(); } var o = new String("Hello My Girl"); o.myComment = "This is Object"; alert( o.myComment ); //"This is Object" alert( o.getLength() ); //13 alert( o ); //"김덕배님의 말 : Hello My Girl" 1. String 객체의 getLength()와 toString()를 오버라이팅 한다...