redux in 14 lines of code

redux-light-example.js

const store = createStore((state = { counter: 0 }, action) => {
  switch(action.type) {
    case "INCREMENT":
      return { counter: state.counter + 1 }
    case "DECREMENT":
      return { counter: state.counter - 1 }
    default:
      return state
  }
})

store.dispatch({ type: "INCREMENT" })
store.dispatch({ type: "INCREMENT" })

console.log(store.getState())

redux-light.js

const createStore = (reducer, state = reducer(undefined, { type: "@@INIT" })) => {
  const subscribers = new Set()
  return {
    dispatch: (action) => {
      state = reducer(state, action)
      subscribers.forEach(func => func())
    },
    subscribe: (func) => {
      subscribers.add(func)
      return () => subscribers.delete(func)
    },
    getState: () => state
  }
}

function createThunkMiddleware(extraArgument) {
  return ({ dispatch, getState }) => next => action => {
    if (typeof action === 'function') {
      return action(dispatch, getState, extraArgument);
    }

    return next(action);
  };
}

const thunk = createThunkMiddleware();
thunk.withExtraArgument = createThunkMiddleware;

export default thunk;