How to detect what class an object in an array is in JavaScript

Question

I'm working on a highly object oriented project in JavaScript. I have an array[] of objects of different classes and I'm iterating through it and I want to check the class of the object at array[i]. Is there any way for me to detect this? This might help you understand what I mean:

var pieces = [new Pawn(), new Rook(), new Knight()];
for(var i = 0; i < pieces.length; i++){
    if(pieces[i] == Rook){
        //Do something with the rook
    }
}

This is the general idea of what I need to do, but the if condition is the tricky bit. How can I detect the class of the element at pieces[i]? My fallback solution is to give every object a "type" field.

bfavaretto · Accepted Answer · 2013-05-08 22:54:44Z

2

This can depend on how you have inheritance set up, but in general you check that with the instanceof operator:

if(pieces[i] instanceof Rook) // ...

answered May 8, 2013 at 22:54

bfavaretto

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1 Comment

RobG Over a year ago

Be careful with instanceof, all it does is check that Rook.prototype is on the private [[prototype]] chain of pieces[i]. That may be OK depending on how you have implemented your inheritance and what you actually need to know. The constructor property might be more suitable (it's a public property so can be set to a suitable value when setting up inheritance initially).

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