ngrx-reducer-immer.ts

import { createAction, createReducer, props } from "@ngrx/store";
import { on } from "ts-action-immer";

const add = createAction("[Todos] Add", props<{ text: string }>());
const reset = createAction("[Todos] Reset");

type Todo = {
  done: boolean;
  text: string;
};
const initialState = {
  todos: [] as Todo[]
};

const reducer = createReducer(
  initialState,
  on(add, (state, { text }) => {
    state.todos.push({
      done: false,
      text
    });
  }),
  on(reset, () => initialState)
);