Key notions

The state is read-only

The only way to change the state is by dispatching an action

UI should be a pure function of the state (React)

The change of states should be done through pure functions that take the previous state, the action and returns the next state : the reducer

Code

Once you created the store passing a reducer, you can getState, dispatch an action and suscribe

Suscribe takes a function as an argument.

This function is launched whenever the state change.

Here is the basic implementation of the createStore function

Composition of reducers helps keeping the reducers isolated

combineReducer is a higher order function that enables to write the former statement in a more concise way.

Here is the implementation of this combineReducers

The id of "presentational component" is to take out the logic from the component and pass it as a parameter

A "container" like FilterLink contains data and presentational componennt

First extract the presentational, then eventually create a container to split between the pure presentational and the store subscription

Connect(mapStateToProps, mapDispatchToProp)(Component) is a way to remove all the mentions to store from the component

Action creators take the important parameter and create the action from it

const { createStore } = Redux

is equivalent to var createStore = Redux.createStore

or import createStore from 'redux.js'

Use Object.assign({},obj, {propertyKey : propertyValue}) to create a new object with the property changed or set.

or the spread operator {...todo, propertyKey:propertyValue}

{todos:todos, visibilityFilter:visibilityFilter} can be written directly {todos, visibilityFilter}

"subscribe" return the function "unsubscribe"

use "expect" library