A **reducer** is a function that receives the action, along with a JavaScript object representing the initial (previous) state, and updates the state if needed. 

A reducer function receives all the actions that are dispatched, it returns a newly updated state object.

In this course, the user will learn how to use Redux and React to create powerful applications.

In this section we will learn what Redux is, why it is useful, and most importantly when it is useful. We will also learn how to set up a basic react-redux application.

In this section we will go through the fundamental concepts of Redux that are necessary to understand the workings of a Redux application. We will use code examples to understand the concepts and in the following section we will use them practically.

In the previous section we looked at the basic concepts. In this section we use those basic concepts to understand some more complicated concepts and the structure of a Redux application. In the end we will also look at the Counter application to put together all the pieces of our knowledge together.

This chapter is focused on practice hence we will utilize the knowledge we acquired in previous sections to create a practical application using Redux along with React.

Redux Reducers