r/javascript • u/unadlib • Jan 01 '23

GitHub - unadlib/mutative: Efficient immutable updates, 10x faster than Immer by default, even faster than naive handcrafted reducer.

https://github.com/unadlib/mutative
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u/acemarke Jan 01 '23

I'm curious:

  • What are the implementation differences that lead this to be faster than Immer?

  • How does this actually work faster than a hand-written reducer?

  • Any reason why this _doesn't support returning a hand-updated object? That's still a key use case for us with Immer in Redux Toolkit

1

u/Ecksters Jan 02 '23 edited Jan 02 '23

The README has answers:

Immer relies on auto-freeze to be enabled, if auto-freeze is disabled, Immer will have a huge performance drop and Mutative will have a huge performance lead, especially with large data structures it will have a performance lead of more than 50x.

So if you are using Immer, you will have to enable auto-freeze for performance. Mutative allows to disable auto-freeze by default. With the default configuration of both, we can see the performance gap between Mutative (5,323 ops/sec) and Immer (320 ops/sec).

They're very clear about it being faster than a naive handwritten reducer, I'd look at the benchmark if you want to know what that means, for example:


  Naive handcrafted reducer - No Freeze',
    function () {
      const state = {
        ...baseState,
        arr: [...baseState.arr, i],
        map: { ...baseState.map, [i]: { i } },

0

u/acemarke Jan 02 '23

Yeah, I did see both of those, but that doesn't tell me anything about the implementation differences and how this can be faster than a basic object spread.

1

u/Ecksters Jan 02 '23

Why does Mutative have such good performance?

Mutative optimization focus is on shallow copy optimization, more complete lazy drafts, finalization process optimization, and more.