Reference to the object, within the object

Question

I was writing a javascript object and to prevent duplication of aliases of the same object

For example, repeating the key for the same values here:

var colours = {
    red: {
        rgb: "255,0,0",
        hex: "#FF0000"
    },
    brickred: {
        rgb: "255,0,0",
        hex: "#FF0000"
    }
};

I tried making a reference to the same object, instead to avoid duplication:

var colours = {
    red: {
        rgb: "255,0,0",
        hex: "#FF0000"
    },
    brickred: this.red
};

However, this does'nt work. I realised (I think) this is because it refers to the window object and not colours. So then I tried:

var colours = {
    red: {
        rgb: "255,0,0",
        hex: "#FF0000"
    },
    brickred: colours.red
};

But this still doesn't work and I don't understand why. How can I solve this?

N.B. The example isn't very good, but basically I have an object literal and want to avoid duplication where I have different keys with same value. I'd also like to know why it doesn't work for curiosity

possible duplicate of [Javascript literal object, reference to itself](http://stackoverflow.com/questions/8347770/javascript-literal-object-reference-to-itself). See also http://stackoverflow.com/questions/4616202/self-references-in-object-literal-declarations or http://stackoverflow.com/questions/4858931/reference-variable-in-object-literal or https://www.google.co.uk/?q=object%20literal%20reference%20self%20javascript — Matt, Feb 19 '14 at 19:48

score 5 · Accepted Answer · answered Feb 19 '14 at 19:48

5

Because at the point of creation the object (including its red key) doesn't exist yet. You can add it afterwards, though:

var colours = {
    red: {
        rgb: "255,0,0",
        hex: "#FF0000"
    }
};

colours.brickred = colours.red;

answered Feb 19 '14 at 19:48

h2ooooooo

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Makes sense and solves the problem - thanks! – user2521439 Feb 19 '14 at 19:50

George Mandis · Answer 2 · 2014-02-20T02:22:26.807

1

I think for you're specific example it might be simpler to encapsulate the object in a separate variable and then apply it to the object, like this:

var _RED = { 
  rgb:"255,0,0", 
  hex:"#ff0000" 
}

var colours = {
  red: _RED,
  brickred: _RED
}

Also, not really what you want for a few reasons, but you could change brickred to a function then you can use this in the manner you originally tried:

var colours = {
    red: {
      rgb: "255,0,0",
      hex: "#FF0000"
    },
    brickred: function() { return this.red; }

};

In this case you could never change the values of brickred and it would have to be called like a function instead of accessed like an attribute, i.e. colours.brickred(). It will always return whatever red is set to.

edited Feb 20 '14 at 02:22

answered Feb 19 '14 at 20:01

George Mandis

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18

1

It should be noted that the last solution would work this way: `colours.red` and `colours.brickred()` (note the `()`) – h2ooooooo Feb 19 '14 at 20:05
You're correct @h2ooooooo. I was aware of this but will update the example to be more clear. – George Mandis Feb 20 '14 at 02:20

Reference to the object, within the object

2 Answers2