building-redux--step-4.js

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

function createStore(reducer){
  // declaring the variable that holds state of the store
  var state
  
  function getState(){
    return state
  }
  
  function dispatch(action){
    // passing the action and the state parameters to the reducer function. The returned value is set as state
    state = reducer(state, action)
  }
  
function subscribe(){
    
    // invoking this returned function will remove the subscriber function
    return function(){
      
    }
    
  }
  
  return {
    getState: getState,
    dispatch: dispatch,
    subscribe: subscribe
  }
}

// testing the dispatch method
const store = createStore(reducer)

// this should set the state to 1
store.dispatch({ type: "INCREMENT" })
console.log(store.getState())

// this should set the state back to 0
store.dispatch({ type: "DECREMENT" })
console.log(store.getState())