creatStore from Scratch

creatStore from Scratch.js

const createStore = (reducer) => {
  let state;
  let listeners = []; // an array of listeners

  const getState = () => state;

  const dispatch = (action) => {
    state = reducer(state, action);
    listeners.forEach(listener => listener()); // to notify every change listener by calling it
  };
  
  const subscribe = (listener) => {
    listeners.push(listener);
    return () => {
      listeners = listeners.filter (l => l !== listener); // unsubscribe the listener that alredy been fired
    };
  };
  
  dispatch({}); // initial state populated dummy action
  
  return { getState, dispatch, subscribe }; // 3 main methods of createStore
};