Creating an associative array in JavaScript

Question

I wasn't sure what to call it for the title,

How can I create an array like this in JavaScript?

var per_kg_list = new Array(
    '03749' => '3.000',
    '03750' => '4.000',
    '03751' => '5.000',
);

basically you are looking for key-value pairs in javascript, you can refer this answer for that stackoverflow.com/questions/7196212/… — AurA
– AurA, Commented Aug 21, 2013 at 5:19
Take a tour of the basics here developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/… — elclanrs
– elclanrs, Commented Aug 21, 2013 at 5:20
The canonical is How to do associative array/hashing in JavaScript. — Peter Mortensen
– Peter Mortensen, Commented Jul 19, 2020 at 20:58

Ruan Mendes · Accepted Answer · 2013-08-21 05:31:41Z

3

You can have an array of objects containing key-value pairs, like this:

var per_kg_list = [
    {'03749': '3.000'},
    {'03750': '4.000'},
    {'03751': '5.000'}
];

Alternatively, you can have an object containing key-value pairs, like this:

var per_kg_list = {
    '03749': '3.000',
    '03750': '4.000',
    '03751': '5.000'
};

edited Aug 21, 2013 at 5:31

Ruan Mendes

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answered Aug 21, 2013 at 5:23

rink.attendant.6

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2 Comments

rink.attendant.6 Over a year ago

What was the purpose of editing my answer to add one whitespace character?

Ruan Mendes Over a year ago

So I could remove my downvote since you updated your answer :)

zs2020 · Accepted Answer · 2013-08-21 05:20:36Z

0

In JavaScript, array doesn't allow to use string as indexes. You may consider to use dictionary:

var per_kg_list = {};
per_kg_list['03749'] = '3.000';
per_kg_list['03750'] = '4.000';
per_kg_list['03751'] = '5.000';

answered Aug 21, 2013 at 5:20

zs2020

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3 Comments

Ruan Mendes Over a year ago

It's just called an object in JS

zs2020 Over a year ago

@JuanMendes Yeah. True.

Ruan Mendes Over a year ago

Also, Array extends Object, so it can be used as map, but you shouldn't. It's really using strings and the keys that parse to integers are taken into account when calculating the length property, more or less Try a=[0]; a["0"] = 1;

Peter Mortensen · Accepted Answer · 2020-07-19 20:59:27Z

0

Someone answered the best way to initializing a JavaScript array with values:

var per_kg_list = {'03749': '3.000', '03750': '4.000', '03751': '5.000'};

edited Jul 19, 2020 at 20:59

Peter Mortensen

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answered Aug 21, 2013 at 5:22

Janith Chinthana

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Comments

Peter Mortensen · Accepted Answer · 2020-07-19 21:00:13Z

0

You can use associative array notations. They are just JavaScript objects with properties:

var set = new Object();
set['Document language'] = 'HTML5';
set['Styling language'] = 'CSS3';
set['JavaScript library'] = 'jQuery';
set['Other'] = 'Usability and accessibility';

edited Jul 19, 2020 at 21:00

Peter Mortensen

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answered Aug 21, 2013 at 5:56

Amarnath

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6 Comments

Ruan Mendes Over a year ago

They are not equivalent

Amarnath Over a year ago

@JuanMendes Okay .. I am just learning JavaScript and this is my first JavaScript answer .. can u pls let me know where is the issue ?

Ruan Mendes Over a year ago

Array extends Object with methods like push, pop, and you would give it numeric indices. If you don't need that behavior, you should just use object.phabricator.com/docs/phabricator/article/…

Ruan Mendes Over a year ago

The comment about the longhand for maps is wrong in the article you linked to, not sure if it's a typo

Ruan Mendes Over a year ago

Here's a link from Google's style guide, explaining why you shouldn't use arrays as associative maps google-styleguide.googlecode.com/svn/trunk/…

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