关于JavaScript的prototype和instanceof

JScript code:

function C1(){}
function C2(){}
C2.prototype=new C1();
function C3(){}
C3.prototype=new C2();
var obj=new C3();
function C4(){}
C3.prototype=new C4();
alert(obj instanceof C2);//true

alert(obj instanceof C1);//true

alert(obj instanceof C3);//false
alert(obj instanceof C4);//false 这个是为什么啊

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谁能帮我解释哈

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JScript code:

function C1(){}
function C2(){}
C2.prototype=new C1();
function C3(){}
C3.prototype=new C2();
var obj=new C3();
function C4(){}
C3.prototype=new C4();
var obj1 = new C3();
alert(obj instanceof C2);//true

alert(obj instanceof C1);//true

alert(obj instanceof C3);//false
alert(obj instanceof C4);//false 这个是为什么啊
alert(obj1 instanceof C2);
alert(obj1 instanceof C4);

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[Quote=引用 1 楼 zhq_442577358 的回复:]
JScript code:

function C1(){}

function C2(){}
C2.prototype=new C1();

function C3(){}
C3.prototype=new C2();

function C4(){}
C4.prototype=new C3();

C2.prototype=new C4();

var obj=new C3();

alert(obj instanceof C2)