Running equation in javascript object

Question

Is it at all possible to run an equation inside an object? An example of what I'd like to achieve is:

var taxes = {
    gst: '0.10',
};

var prices = {
    first_key: '437.95',
    total_key: parseFloat(prices.first_key * taxes.gst).toFixed(2),
    .......
    },
};

Or am I going to have to run it through as a function?

var prices = {
    total_key: function() { return parseFloat(prices.first_key * taxes.gst).toFixed(2);}
}

If at all, is it possible to do it as the first option?

Cheers.

The expression in the first example will be executed when you do the `var prices` assignment, not every time you access the element. — Barmar, Nov 11 '14 at 00:48
There's no point in calling `parseFloat()` on the result of a multiplication. You should call `parseFloat` on the strings that are in the properties _before_ multiplying them. — Barmar, Nov 11 '14 at 00:49
Have tested it, it seems the answers solve the issue I was facing. Also thanks @Barmar for that note! — Darren, Nov 11 '14 at 00:52
possible duplicate of [Self-references in object literal declarations](http://stackoverflow.com/questions/4616202/self-references-in-object-literal-declarations) — Qantas 94 Heavy, Nov 11 '14 at 01:07

score 2 · Accepted Answer · answered Nov 11 '14 at 00:49

2

Use javascript object getters.

var prices = {
    first_key: '437.95',
    get total_key(){return parseFloat(this.first_key * taxes.gst).toFixed(2)},
    .......
    },
};

then to access value,

prices.total_key

answered Nov 11 '14 at 00:49

Sampath Liyanage

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score 1 · Answer 2 · answered Nov 11 '14 at 00:50

You can setup a getter function, which pretty much is a function, but behaves as a property. That could look like

var prices = {
    first_key: '437.95',
    get total_key() {
        return (parseFloat( this.first_key ) * parseFloat( taxes.gst ) ).toFixed( 2 );
    }
};

Now you can just access

prices.total_key;

and you get the result.

Running equation in javascript object

2 Answers2