Redux!

Quick review of core redux concepts

1. State Tree
   • Everything that changes in the application including data and UI states are stored in single object called state or state tree.
   • Is minimal representation of App
2. State can only change by action
   • State is READ ONLY
   • Can be change by only dispatching an action
   • Action is a JavaScript object, describing in a minimal way what changed in an application
3. Pure functions
   • Should not do network call, db call, update DOM etc..
   • Should not modify the object that is passed.
4. Reducer Function
   • Takes previous state, action being dispatched and returns new state of the app
   • Has to be pure function
5. Properties of a reducer function
   • Should accept state and action as argument
   • Should return current state in case un-handled event type is recieved
   • Should return default state in case state is undefined.

example for a reducer

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