this.objectProperty is undefined inside object literal

Question

I've been working with object literals for a while now but I'm stumped as to why the object property is returning undefined when accessing it using this here's an example of what I am trying to do...

var x = (function(){
    return{
        a: "1",
        b : this.a
    };
})();

console.log(x.b);

what am I doing wrong here?

Answer 1

Use a function to return the object, which will assign the invoking object to this

var x = (function(){
    return{
        a: "1",
        b : function(){return this.a;}
    };
})();

JS Fiddle: http://jsfiddle.net/AFtT5/1/

You could also use a get method:

var x = (function(){
    return{
        a: "1",
        get b (){return this.a;}
    };
})();

console.log(x.b);

JS Fiddle: http://jsfiddle.net/AFtT5/2/

Answer 2

The value of this is determined by how the currently executing function was called.

In this case, it will probably be window (if you are running in a browser and not in strict mode)

There is no way to refer to an object, constructed using an object literal, while it is being constructed.

You have to do it in two steps.

var x = (function(){
    var obj = {
        a: "1",
    };
    obj.b = obj.a;
    return obj;
})();

console.log(x.b);