Question

I have a JavaScript array inside a namespace like this:

app.collec.box = [];

and I have a function inside the same namespace like this:

app.init = function () {
    var box = this.collec.box;
    // ... code to modify box
};

I thought that setting a local variable equal to an object or object property was just a REFERENCE to the original, but it seems I am wrong, after changing the contents of the local box variable inside my function, app.collec.box does not change.

Please help, what am I doing wrong? how can I solve this?

Thanks in advance.

EDIT. This is the complete code.

var app = {
    collec: {
        box: [],
        cache: []
    },

    init: function () {
        var box = this.collec.box;

        $.ajax({
            url: 'file.json',
            success: function (json) {
                // Map JSON array to box array using Underscore.js _()map
                box = _(json).map(function (o) {
                    return new Model(o);
                });
            }
        });
    }
};

app.init();

Answer 1

References point to objects, not variables. box is not a reference to the variable this.collec.box; rather, box and this.collec.box are references to one specific object in memory. You can modify the properties of this object through either of these variables, but you can’t use one variable to modify another variable.

If you want to modify what this.collec.box refers to, you either need to set it directly like this:

this.collec.box = ...;

or use a reference to the this.collec object and modify its box property:

var x = this.collec;
x.box = ...;

---

Edit: Maybe a couple of diagrams will make it easier to understand what’s happening.

When you assign box = this.collec.box, this is what actually happens:

this.collec.box -----> (object) <----- box

Both the variables point to the same object in memory, but in no way does box actually refer to the this.collec.box variable.

What you are expecting would work if this happened:

box -----> this.collec.box -----> (object)

but this doesn’t happen.