■スクリプト
<HTML> <HEAD> <TITLE>prototype</TITLE> </HEAD> <BODY bgColor="white"> <CENTER> <H1>プロパティの追加</H1> </CENTER> <SCRIPT Language="JavaScript"> <!-- Math.prototype.myBirthday = "1969/02/15"; theMath = new Math(); alert(theMath.myBirthday); // --> </SCRIPT> </BODY> </HTML>