CODEWITHSUNDEEP
immutable.js
knagode
knagode

Reputation: 6125

immutable.js get keys from map/hash

I want to retrieve keys() from the following Immutable Map:

var map = Immutable.fromJS({"firstKey": null, "secondKey": null });
console.log(JSON.stringify(map.keys()));

I would expect the output:

["firstKey", "secondKey"]

However this outputs:

{"_type":0,"_stack":{"node":{"ownerID":{},"entries":[["firstKey",null],["secondKey",null]]},"index":0}}

How to do it properly?

JSFiddle link: https://jsfiddle.net/o04btr3j/57/

Upvotes: 26

Views: 29515

Answers (4)

josephemswiler
josephemswiler

Reputation: 521

Best practice with Immutable.js is to use Immutable data structures and minimize conversions to JavaScript types. For this problem we can use keySeq(), which returns a new Seq.Indexed (an ordered indexed list of values) of the keys of this Map. We then can then set a List to those values and assign that List to a variable for use later. Here is an example of how this solution could be implemented:

import { Map, List } from 'immutable';

const exampleMap = Map({ a: 10, b: 20, c: 30 });

const keys = List(exampleMap.keySeq()); // List [ "a", "b", "c" ]

Upvotes: 1

atomictom
atomictom

Reputation: 1807

Possibly just answering my own question that lead me here, but I found mapKeys() which will gives you access to keys in a regular loop. It seems a bit more "the right way". (The docs are so vague, who knows!)

eg:

Map({ a: 1, b: 2 }).mapKeys((key, value) => console.log(key, value))
// a 1
// b 2

Upvotes: 3

lumio
lumio

Reputation: 7575

Although this question got answered a while ago, here is a little update:

ES6 Solution: 

const [ ...keys ] = map.keys();

Pre ES6 Solution: 

var keys = map.keySeq().toArray();

Upvotes: 48

Sagi Medina
Sagi Medina

Reputation: 915

This is how ImmutableJS object looks like.

If you want to get:

["firstKey", "secondKey"]

You need to do:

console.log(map.keySeq().toArray())

Upvotes: 39

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