Inject variables of parent context in function - JavaScript

Question

I'm developing a micro MV* Framework for JavaScript and came upon the idea to introduce computed properties like it's done in Ember.js

What I basically want is something like this:

_defaults: {
    firstEarning: 5,
    secondEarning: 1200.75,
    paycheck: function(firstEarning, secondEarning) {
        return firstEarning + secondEarning;
    }.inject('firstEarning', 'secondEarning')
}

When I want to retrieve paycheck then the values of firstEarning and secondEarning should be injected into the function.

I tried to extend the Function prototype, but realized that I don't have the context pointing to the object where _defaults lives.

I tried to understand what Ember.js did to achieve this, but I didn't really get it.

Has anybody here an idea how to achieve this?

Answer 1

... I think you're really over-thinking this.

Just use this :

_defaults: {
    firstEarning: 5,
    secondEarning: 1200.75,
    paycheck: function() {
        return this.firstEarning + this.secondEarning;
    }
}