Creating some associative array in JavaScript

Question

I have an object which contains an array, and I want it to contain an associative array so keys are strings. How can I do it?

This does not work:

{profiles: { easy:["example" : 1], advanced:["example" : 1] }

I wanted to avoid

console.log({profiles: { easy: {"example": 1}, advanced:{"example": 1} })

Because that easy and advanced members are not displayed as an array but as an object.

Another way I know is this:

array['key2'] = 'new value';

but that is not part of the object, so I would need to split the command for multiple lines - which is not what I want.

PHP has something like array("mykey" => "myValue"), but does JavaScript have something similar?

Yet I don't want to use frameworks. This is JavaScript only.

As does @HectorBarbossa says, you will have to do this with objects : `{"yourKey": 42.314}` — boehm_s, Jul 12 '16 at 22:05
The canonical is *[How to do associative array/hashing in JavaScript](https://stackoverflow.com/questions/1208222)*. — Peter Mortensen, Jul 19 '20 at 20:57

score 11 · Accepted Answer · answered Jul 12 '16 at 22:07

JavaScript doesn't have "associative arrays".

It has objects, which you can store values on in named properties.

It has arrays, which store an ordered set of values via integer properties. Since they are a type of object, you can also store named values on them (but you can't create them using the literal syntax, only add them after the array is created) but this isn't considered good practise and they will be ignored by just about anything that has special case handling for arrays.

As of ES6 it also has Maps which are similar to objects in that you can give them named values, but also to arrays in that order is preserved. There is no literal syntax for creating a Map.

score 3 · Answer 2 · edited Jul 19 '20 at 20:35

3

wanted to avoid console.log({profiles: { easy:{"example" : 1},advanced:{"example" : 1} })

Why? Is there a reason to avoid language-specific features?

If I told you you can do this (should be avoided):

var array = [];
array["foo"] = "bar";
array.foo // -> bar

The problems with it:

array.length // -> 0

So, even if you can apply properties to mostly everything in JavaScript like:

var str = "hello";
str.type = "greetings";

you shouldn't screw the language...

This is the normal way of creating key:value maps, objects:

var obj = {foo: "bar"}
obj.foo // -> bar

Why not do it just like the language is designed to?

edited Jul 19 '20 at 20:35

Peter Mortensen

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answered Jul 12 '16 at 22:08

webdeb

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"this is the same" — They are not the same. There are many differences between arrays and objects, even if you put a property called "foo" on each of them. – Quentin Jul 12 '16 at 22:08
@Quentin you are right I added your remark to my answer – webdeb Jul 12 '16 at 22:13
For me it is better to use [] because I know that I plan to use it like array not like object. Even that the choice of object would be shorter definition. It is all about to make the things clear for me when I create the final object (wrapper). – John Boe Jul 12 '16 at 22:18
@user1141649 — You plan to use named keys, that is not "like an array". – Quentin Jul 12 '16 at 22:19
@user1141649 you cannot use it like an array this way, the length would be still 0 for example.. see edits – webdeb Jul 12 '16 at 22:42

Creating some associative array in JavaScript

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