How to use ES6 Hash Map on any object without maintaing a reference (I.e. Java hashcode)

Question

I've been experimenting with ES6 Map in io.js and realized that I can't do the following:

var map = new Map()
map.set( {key:"value"}, "some string");
map.get( {key:"value"} ); // undefined. I want "some string"

This is because {key:"value"} === {key:"value"} is false.

I need to be able to use an object as a key but not require the ACTUAL object to lookup the value like how java HashMap uses hashcode and equals. Is this possible?

If you are prepared to go all-in with Immutable.js, you can use Record as complex key for immutable Map. immutable-js.github.io/immutable-js — rpggio
– rpggio, Commented Oct 25, 2020 at 19:53

the8472 · Accepted Answer · 2015-02-06 14:12:31Z

8

If the lack of object identity stems from a serialize-deserialize roundtrip just give them a unique ID that survives that and use that ID as key
calculate a key from a subset of its properties if you can be certain that the remaining properties either depend on that subset or are irrelevant to your operation
implement your own hash map and object hashing. this can get tricky with host objects but should be fairly simple with JSON-compatible data
JSON-encode before each get or set. It's quite inefficient and only works with JSON-serializeable objects. But easier to implement than the previous option

edited Feb 6, 2015 at 14:12

answered Feb 6, 2015 at 11:47

the8472

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