npm install redux

import { createStore } from "redux"

/**
 * This is a reducer - a function that takes a current state value and an
 * action object describing "what happened", and returns a new state value.
 * A reducer"s function signature is: (state, action) => newState
 *
 * The Redux state should contain only plain JS objects, arrays, and primitives.
 * The root state value is usually an object. It"s important that you should
 * not mutate the state object, but return a new object if the state changes.
 *
 * You can use any conditional logic you want in a reducer. In this example,
 * we use a switch statement, but it"s not required.
 */
function counterReducer(state = { value: 0 }, action) {
 switch (action.type) {
 case "counter/incremented":
 return { value: state.value + 1 }
 case "counter/decremented":
 return { value: state.value - 1 }
 default:
 return state
 }
}

// Create a Redux store holding the state of your app.
// Its API is { subscribe, dispatch, getState }.
let store = createStore(counterReducer)

// You can use subscribe() to update the UI in response to state changes.
// Normally you"d use a view binding library (e.g. React Redux) rather than subscribe() directly.
// There may be additional use cases where it"s helpful to subscribe as well.

store.subscribe(() => console.log(store.getState()))

// The only way to mutate the internal state is to dispatch an action.
// The actions can be serialized, logged or stored and later replayed.
store.dispatch({ type: "counter/incremented" })
// {value: 1}
store.dispatch({ type: "counter/incremented" })
// {value: 2}
store.dispatch({ type: "counter/decremented" })
// {value: 1}