bedit

Silly (but lowkey kinda good?) idea for a immer-like tool that is super lightweight (and probably faster?) but most importantly doesn't pollute your stack frames with Proxies.

Example

type Todo = {
  id: string;
  title: string;
  completed: boolean;
};

type AppState = {
  todos: Todo[];
  filter: "all" | "active" | "completed";
};

const baseState: AppState = {
  todos: [
    { id: "1", title: "Buy milk", completed: false },
    { id: "2", title: "Clean the bath", completed: false },
  ],
  filter: "all",
};

immer

const nextState = produce(baseState, (draft) => {
  // draft is a proxy (boo)
  draft.todos[1].completed = true;
});

bedit

const nextState2 = edit(baseState).todos[1]((todo) => {
  // todo is a regular ass JS object, via structuredClone
  todo.completed = true;
});

// or just
const nextState3 = edit(baseState).todos[1].completed(true);

Drawbacks

The main api issue is that it does a deep structuredClone on the target object by default, so if you want to do minimum copying while making multiple edits you'd need to be aware of the shallow option.

const nextState4 = edit(baseState, {shallow: true})(state => {
  state.filer = 'active'
  state.todos = edit(state.todos)[0].completed(true)
})

It's also just a little weird as an API, but I reckon people would get used to it pretty quickly. Plus with TS and Object.freeze at dev time I reckon it could be pretty on-rails?