function parent(){
this.x=10;
}
function child(){
var parentObj=new parent();
for(var p in parentObj)this[p]=parentObj[p];
}
var childObj=new child();
alert(childObj.x);

function parent(){
this.x=10;
}
function child(){
this.parent=parent;
this.parent();
delete this.parent;
}
var childObj=new child();
alert(childObj.x);

function parent(){
this.x=10;
}
function child(){
parent.call(this);
}
var childObj=new child();
alert(childObj.x);

function parent(){
}
parent.prototype.x=1;

function child(){
}
for(var p in parent.prototype)child.prototype[p]=parent.prototype[p];
child.prototype.y=2;

var childObj=new child();
alert(childObj.x);

function parent(string){
var child=new Function("this.x=10;"+string);
return child;
}
var child=new parent("this.y=20;");

var childObj=new child();
alert(childObj.y);

function parent(){
this.x=10;
}
function child(){
}
child.prototype=new parent();
var childObj=new child();
alert(childObj.x);

function parent(){
this.x=10;
}
function child(){
var ret=new parent();
ret.y=20;
return ret;
}

var childObj=new child();
alert(childObj.x);