mutitmut

Mutate immutable data.

Well that doesn't really make sense. What it really does is mutate data, cloning only objects that are mutated and re-using all other objects.

It can be summed up like this.

• It does not clone objects that do not need to mutate.
• It clones and applies changes to objects that do need to mutate; the modified object and its ancestors.

Why

The driver was redux reducers, with their requirements for pure functions, with no side effectsand no mutations.

Libraries like Immutable or mori provide an relatively easy means of managing immutable data, but referencing such data in React component can be a little noisy.

Using mutitmut means that React components can be provided with data that is easy to use. It is just regular JavaScript objects. Yet it is still suitable for shallow equality testing in shouldComponentUpdate implementations.

Examples

Set or update a value somewhere in an object graph. Specify the path either as an array, or in dotted string.

  import {set, update} from 'mutimut';

  const state = {
    array : [1, 2, 4, 8],
    nested: {a: 1, b: 2}
  };

  const state2 = set(state, ['nested', 'b'], 20);
  // { array: [1, 2, 4, 8], nested: {a: 1, b: 20} }

  const state3 = set(state, 'nested.b', 30);
  // { array: [1, 2, 4, 8], nested: {a: 1, b: 30} }

  const state2 = update(state, ['nested', 'b'], value => value + 3);
  // { array: [1, 2, 4, 8], nested: {a: 1, b: 5} }

Note that in all cases new state and nested objects have been created. However the array is not cloned; the original one is kept.

API

Set

  import {set} from 'mutimut';

  set(data, path, value) // => new data

Arguments

• data (Object): The object graph to be modified.
• path (Array|String): The path in data to the value to be modified.
• value (any) : The value to be set in data at the specified path.

Returns

(Object): The modified object graph.

Update

  import {update} from 'mutimut';

  update(data, path, mutator) // => new data

Arguments

• data (Object): The object graph to be modified.
• path (Array|String): The path in data to the value to be modified.
• mutator (Function) : A function that accepts the old value and returns the new one to set.

Returns

(Object): The modified object graph.