How to use an exist property in object [duplicate]

Question

I'm trying this

var a = {
    "a" : "Hey",
    "b" : this.a + "!"
};

console.log(a.b);

==>"undefined!"

but if I use this it works fine.

var a = {};
a.a = "haha";
a.b = a.a + "!";

console.log(a.b);

==>"haha!" 

How can I use the first way to make it work?

Answer 1

this doesnt exist in that context of an Object literal. You will have to write a.a instead of this.a. However, while inside a function which is defined in the object, this actually refers to the object itself.

This has to do with JavaScripts referencing environments.