pure reducer with map && filter (not complete)

reducer.example.js

let array = [1,2,3,4]

function reducer(state , action){
  switch(action.type){
    case "remove":
      return state.filter(function(elem , index){
        return index != action.id
      })
    case 'inc':
    	return state.map(function(elem , index){
    		return (index == action.id) ? elem + 1 : elem
    	})
  }
}

action0 = {
  type : 'remove', 
  id : 0
}

action1 = {
  type : 'remove', 
  id : 1
}

action2 = {
  type : 'inc', 
  id : 2
}

action3 = {
  type : 'inc', 
  id : 3
}

action0 = {
  type : 'inc', 
  id : 0
}

action1 = {
  type : 'inc', 
  id : 1
}

action2 = {
  type : 'inc', 
  id : 2
}

action3 = {
  type : 'remove', 
  id : 3
}