1.类抄写

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);

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2.类冒充

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);

?

3.原型抄写

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);

?4.元类继承

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);

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?5.原型继承

5.1引用型原型继承

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

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5.2复制型原型继承

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

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

??