Initializing object properties with objects own properties

Question

I get the error:

Uncaught TypeError: Cannot read property 'interval' of undefined

When I try to initialize an object like this:

var loop = {
    interval: 5 * 1000,
    maxInterval: loop.interval * 12
};

So instead I have to do it like this:

var loop = {
    interval: 5 * 1000
};
loop.maxInterval = loop.interval * 12;

Is there a better way of doing this?

Define "better". There are certainly other ways, but unless there are some criteria for evaluation (faster, easier to read, extensible, etc.), who is to say one is "better" than another except by subjective opinion? ;-) — RobG
– RobG, Commented Jul 25, 2015 at 0:04

Raffaele · Accepted Answer · 2015-07-25 00:04:24Z

1

No way.

But conceptually all you need is moving the constant one level up:

var defaultInterval = 5000;
var loop = {
    interval: defaultInterval,
    maxInterval: defaultInterval * 12
};

answered Jul 25, 2015 at 0:04

Raffaele

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Comments

plarner7 · Accepted Answer · 2015-07-25 00:03:48Z

0

One option is using self executing function.

var loop = (function () {
    var _ = {};

    _.interval         = 5 * 1000;
    _.maxInterval      = _.interval * 12;

    return _;
})();

answered Jul 25, 2015 at 0:03

plarner7

1256 bronze badges

Actually probably var loop = {}; loop.interval = 5 * 1000; loop.maxInterval = loop.interval * 12; is best.