Performance

Mutative is a high-performance immutable data structure library, it is up to 2x-6x faster than naive handcrafted reducer and up to 16x faster than Immer.

Mutative vs Reducer Performance

Reducer by object

• Naive handcrafted reducer

// baseState type: Record<string, { value: number }>
const state = {
  ...baseState,
  key0: {
    ...baseState.key0,
    value: i,
  },
};

• Mutative

const state = create(baseState, (draft) => {
  draft.key0.value = i;
});

Measure(seconds) to update the 1K-100K items object, lower is better(view source).

Mutative is up to 2x faster than naive handcrafted reducer for updating immutable objects.

Reducer by array

• Naive handcrafted reducer

// baseState type: { value: number }[]

// slower 6x than Mutative
const state = [
  { ...baseState[0], value: i },
  ...baseState.slice(1, baseState.length),
];

// slower 2.5x than Mutative
// const state = baseState.map((item, index) =>
//   index === 0 ? { ...item, value: i } : item
// );

// same performance as Mutative
// const state = [...baseState];
// state[0] = { ...baseState[0], value: i };

The actual difference depends on which spread operation syntax you use.

• Mutative

const state = create(baseState, (draft) => {
  draft[0].value = i;
});

Measure(seconds) to update the 1K-100K items array, lower is better(view source).

Mutative is up to 6x faster than naive handcrafted reducer for updating immutable arrays.

Mutative vs Immer Performance

Mutative passed all of Immer's test cases.

Measure(ops/sec) to update 50K arrays and 1K objects, bigger is better(view source). [Mutative v1.1.0 vs Immer v10.1.1]

Naive handcrafted reducer - No Freeze x 4,670 ops/sec ±0.64% (96 runs sampled)
Mutative - No Freeze x 6,747 ops/sec ±0.61% (95 runs sampled)
Immer - No Freeze x 5.65 ops/sec ±1.53% (19 runs sampled)

Mutative - Freeze x 1,062 ops/sec ±0.74% (95 runs sampled)
Immer - Freeze x 394 ops/sec ±0.85% (93 runs sampled)

Mutative - Patches and No Freeze x 1,011 ops/sec ±0.24% (98 runs sampled)
Immer - Patches and No Freeze x 5.64 ops/sec ±0.22% (19 runs sampled)

Mutative - Patches and Freeze x 545 ops/sec ±1.19% (94 runs sampled)
Immer - Patches and Freeze x 215 ops/sec ±0.70% (86 runs sampled)

The fastest method is Mutative - No Freeze

Run yarn benchmark to measure performance.

OS: macOS 14.7, CPU: Apple M1 Max, Node.js: v22.11.0

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 is disabled auto-freeze by default. With the default configuration of both, we can see the 17x performance gap between Mutative (6,747 ops/sec) and Immer (394 ops/sec).

Overall, Mutative has a huge performance lead over Immer in more performance testing scenarios. Run yarn performance to get all the performance results locally.

More Performance Testing Scenarios

Mutative is up to 2.5X-82.9X faster than Immer:

view source.