CODEWITHSUNDEEP
javascriptoop
user1801625
user1801625

Reputation: 1223

How can I know which object I inherit

In javascript how can I know which object I inehrit? for example

function a() {
    this.c = 1;
}

function b() {
    this.d = 2;
}
b.prototype = new a();​

How can I check that b inherit from a?

Thank you.

Upvotes: 2

Views: 68

Answers (4)

Mark Porter
Mark Porter

Reputation: 1630

of you probably want instanceOf. 

if (b instanceOf a) {
    console.log("b is instance a")
}

This also has the advantage of walking the whole prototype chain so it does not matter if it is a parent, grandparent, etc

Upvotes: 0

zzzzBov
zzzzBov

Reputation: 179246

Use the instanceof operator:

//capital letters indicate function should be used as a constructor
function A() {...}
function B() {...}
B.prototype = new A();
var a,
    b;
a = new A();
b = new B();

console.log(a instanceof A); //true
console.log(a instanceof B); //false
console.log(b instanceof A); //true
console.log(b instanceof B); //true
console.log(B.prototype instanceof A); //true

Upvotes: 2

Billy Moon
Billy Moon

Reputation: 58619

Use the constructor property of b.prototype or any instance of b.

function a(){
  this.c=1;
}

function b(){
  this.d=2;
}

b.prototype=new a();

x = new b()

if(x.constructor == a){
    // x (instance of b) is inherited from a
}

Upvotes: 1

lostsource
lostsource

Reputation: 21840

Try this

 b.prototype.constructor.name

Working example: http://jsfiddle.net/psrcK/

Upvotes: 1

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