markSimpleObject()

markSimpleObject is a mark that makes simple objects draftable: plain objects, objects without a prototype, such as those of Object.create(null), and plain objects of other realms, such as same-origin iframes or vm contexts, whose prototype is that realm's Object.prototype. Without it, Mutative drafts only plain objects of its own realm, and create() throws for a base state of the other kinds.

markSimpleObject(value: unknown): 'immutable' | undefined

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Pass it as the mark option, of a call or of makeCreator():

import { create, markSimpleObject } from 'mutative';

const baseState = {
  foo: {
    bar: 'str',
  },
  simpleObject: Object.create(null),
};

const state = create(
  baseState,
  (draft) => {
    draft.foo.bar = 'new str';
    draft.simpleObject.a = 'a';
  },
  {
    mark: markSimpleObject,
  }
);

expect(state.simpleObject).not.toBe(baseState.simpleObject);
expect(state.simpleObject.a).toBe('a');
expect(Object.getPrototypeOf(state.simpleObject)).toBe(null);
expect(baseState.simpleObject.a).toBe(undefined);

It returns 'immutable' for simple objects and nothing for other values, which Mutative then drafts as usual, so it combines with other marks in an array, as in mark: [markSimpleObject, markClasses]. Like any immutable mark, it works with patches and auto-freeze.