function Parent(){}
Parent.prototype.say = function () {
return 20;
};
function Child(){
}
Child.prototype.say = function () {
return 10;
};
inherit(Child, Parent);
function inherit(C, P) {
C.prototype = P.prototype;
}
var parent = new Parent();
var child = new Child();
var child2 = new Child()
alert(child.say(); //20
alert(parent.say()); //20
alert(child2.say()); //20