How does Javascript associative array work?

Question

I am in bit of a puzzle, recently I had worked on a project where use of javascript was necessary. Everything is working fine I just need to know how does it work

eg : I had a dynamic variable count, which use to get some value, lets say I get the value as var count = 6;

Now when I put this in array {count : count } I get the output as {count : 6}

Now my doubt is the output should have been { 6 : 6} as count should have been replaced with its value but it didn't happen so. Why is happening ? and how is this working properly ?

In JavaScript, that is called an object literal and it functions differently from what you may have come to understand with PHP's associative arrays. If that is literally your code {count: count} then you have assigned the variable count on the right to the key count on the left. If you had used something like theObj[count] = count, then you would have ended up with the {6: 6} you expected. — Michael Berkowski
– Michael Berkowski, Commented Jun 1, 2014 at 12:42
Please post the code with more context so we can see what you attempted. — Michael Berkowski
– Michael Berkowski, Commented Jun 1, 2014 at 12:42
You are referencing the variable with it's value in the format javascript wants it. The language just interprets it that way. Try giving us a concrete example — Hristo Georgiev
– Hristo Georgiev, Commented Jun 1, 2014 at 12:44
@MichaelBerkowski Thanks for the descriptive answer, I think I get it what you said — Anand Joshi
– Anand Joshi, Commented Jun 1, 2014 at 12:45

ColBeseder · Accepted Answer · 2014-06-01 12:42:20Z

1

The key value pairs treat the key as a literal and the value as a variable.

so:

var count = 6;
var o = {count: count};  // results in {count: 6}

but to use a variable as the key, you can do this:

var count = 6;
var o = {};
o[count] = count;  // results in: {6: 6}

answered Jun 1, 2014 at 12:42

ColBeseder

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mystery · Accepted Answer · 2014-06-01 12:42:29Z

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The JavaScript object initialisation syntax lets you use bare words. If you do this:

{ foo: 6, bar: 12 }

It's equivalent to this:

{ 'foo': 6, 'bar': 12 }

What you want is to assign directly, like so:

var foobar = {};
foobar[foo] = 6;
foobar[bar] = 12;

answered Jun 1, 2014 at 12:42

mystery

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Zaenille · Accepted Answer · 2014-06-01 12:42:56Z

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In JavaScript associative arrays (or most associative arrays for that matter), the left side is the key, and the right side is the value. -> {key:value}

When you put {count:count} when you have a count variable beforehand (let's say its value is 10), what will happen is it will be read as {count:10}.

The left-hand side, or the key, is not a variable, but a constant.

answered Jun 1, 2014 at 12:42

Zaenille

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