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 http://stackoverflow.com/questions/7196212/how-to-create-dictionary-and-add-key-value-pairs-dynamically-in-javascript — AurA, Aug 21 '13 at 05:19
Take a tour of the basics here https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Values,_variables,_and_literals#Object_literals — elclanrs, Aug 21 '13 at 05:20
The canonical is *[How to do associative array/hashing in JavaScript](https://stackoverflow.com/questions/1208222)*. — Peter Mortensen, Jul 19 '20 at 20:58

score 3 · Accepted Answer · edited Aug 21 '13 at 05:31

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 '13 at 05:31

Ruan Mendes

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answered Aug 21 '13 at 05:23

rink.attendant.6

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What was the purpose of editing my answer to add one whitespace character? – rink.attendant.6 Aug 21 '13 at 05:32
4

So I could remove my downvote since you updated your answer :) – Ruan Mendes Aug 21 '13 at 05:34

score 0 · Answer 2 · answered Aug 21 '13 at 05:20

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 '13 at 05:20

zs2020

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It's just called an object in JS – Ruan Mendes Aug 21 '13 at 05:26
@JuanMendes Yeah. True. – zs2020 Aug 21 '13 at 05:29
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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;` – Ruan Mendes Aug 21 '13 at 05:51

score 0 · Answer 3 · edited Jul 19 '20 at 20:59

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 '20 at 20:59

Peter Mortensen

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answered Aug 21 '13 at 05:22

Janith Chinthana

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score 0 · Answer 4 · edited Jul 19 '20 at 21:00

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 '20 at 21:00

Peter Mortensen

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answered Aug 21 '13 at 05:56

Amarnath

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They are not equivalent – Ruan Mendes Aug 21 '13 at 06:00
@JuanMendes Okay .. I am just learning JavaScript and this is my first JavaScript answer .. can u pls let me know where is the issue ? – Amarnath Aug 21 '13 at 06:07
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.http://www.phabricator.com/docs/phabricator/article/Javascript_Object_and_Array.html – Ruan Mendes Aug 21 '13 at 07:49
The comment about the longhand for maps is wrong in the article you linked to, not sure if it's a typo – Ruan Mendes Aug 21 '13 at 07:54
If you just change your code to say `=new Object ()` or `={}`, then it would be correct. Your code will work but you should understand the difference between object and arrays – Ruan Mendes Aug 21 '13 at 07:58
1

Here's a link from Google's style guide, explaining why you shouldn't use arrays as associative maps http://google-styleguide.googlecode.com/svn/trunk/javascriptguide.xml?showone=Associative_Arrays#Associative_Arrays – Ruan Mendes Aug 23 '13 at 19:46

Creating an associative array in JavaScript

4 Answers4