The whole state of your app is stored in an object tree inside a single store. The only way to change the state tree is to emit an action, an object describing what happened. To specify how the actions transform the state tree, you write pure reducers. import { createStore, combineReducers } from "redux" ; /** * This is reducer, a pure function with (state,action) => state signature. * It describes how an action transforms the state into the next state. * * The shape of the state is up to you: it can be a primitive, an array, an object, * or even an Immutable.js data structure. The only important part is that you should * not mutate the state object, but return a new object if the state changes. * * In this example, we use a `switch` statement and strings, but you can use a helper that * follows a different convention (such as function maps) if it makes sense for your * project. */ // User operation reduc...