React Router Quick Start Guide

Reducers

A Reducer in Redux alters the state of an entity based on the action dispatched to the store. A Reducer is a pure function that accepts two parameters: state and action. The Reducer then returns an updated state based on the value store in action.type. For example, consider the following reducer:

const todoReducer = (state = [], action) => {    switch (action.type) {        case 'ADD_TODO':            return [                ...state,                {                    id: action.payload.id,                    text: action.payload.text,                    isCompleted: action.payload.isCompleted                }            ];        default:            return state;    }}

The initial state of todoReducer is set to an empty array (state parameter's default value) and a TODO is added to the list when the action type is ADD_TODO. One of the core tenets of Redux is not to mutate the state ...