The prototype property allows you to add new properties and methods to the Boolean object that can be used throughout your code.
The following example assigns a New Method to the Boolean Object with the prototype Property.
<html>
<script language="JavaScript">
<!-- function letterBoolean() { if(this == true) return("T"); else return("F");
}
//Make the letterBoolean function available to all Boolean objects
Boolean.prototype.letter = letterBoolean;
var myBooleanObj = new Boolean(true);
document.write("myBooleanObj is set to ",myBooleanObj.letter());
-->
</script>
</html>