sampleReducer.js

var x = /\s/g;
var y = /(.{4})/g;

const initialState = {
  number: ''
}
//console.log(initialState)
function reducer(state = initialState, action) {
  console.log("current state is ", state, "current action is ", action);
  switch(action.type) {
    case PROCESS_NUMBER:
      return {
        ...state,
        number: action.payload.replace(x, '').replace(y, '$1 ')
      }
      console.log("this is the current state", state)
    default:
      return state;
  }
}
const PROCESS_NUMBER = 'PROCESS_NUMBER';

function processAction(payload) {
  return {type: PROCESS_NUMBER, payload}
}

//console.log(reducer(null, processAction("9999999999999") ))
reducer(null, processAction("4555555"))