What is Redux? Store, Actions, and Reducers Explained for Beginners

Most libraries, such as React and Angular, are built with a way for components to internally manage their state without the need for an external library or tool. This works well for applications with few components, but as an application grows larger, managing states shared across components becomes a hassle. Redux is used to maintain and update data across your applications for multiple components to share, all while remaining independent of the components. The state of the whole application is stored in the form of a JS object tree in a single store as shown below. We will also see how some of its core building blocks work, such as store, actions, and reducers and how they all come together and make Redux the global state management library that it is.

• You can think of an action as an event that describes something that happened in the application.
• Remember to return new state objects, instead of mutating the previous state.
• You can think of it as “reducing the array down to one value”.

For this example, we have chosen geojs.io and the Wikipedia API, which are easy enough to access for our purpose. The previous version, react-redux v6, brought support for the new React Context API to the package. However, there were some important performance issues that have been solved with the release of v7. The first time that the callback runs, there isn’t a previousResult available, so we need to also pass in an initial value that will be used as the first previousResult. We’ll talk more about the rules of reducers later, including why they’re important and how to follow them correctly.

Redux Components

Use Vitest to write tests with practical examples and strategies, covering setting up workflows, mocking, and advanced testing techniques. One major benefit of Redux is the ability to navigate through the state’s history, allowing developers to observe how the state has changed throughout the app’s lifecycle. However, it is important to implement Redux only if it fits your requirements and your project needs a state management tool.

As the application has complex programming and works then managing the state also becomes complex until we have management or control over the state of the application. So, for this reason, we have to maintain the state of the application. This can happen in the following steps which are known as the redux workflow.

Why Should I Use Redux?​

Whenever an action is dispatched, all the reducers are activated. Each reducer filters out the action using a switch statement switching on the action type. Whenever the switch statement matches with the action passed, the corresponding reducers take the necessary action to make the update and return a fresh new instance of the global state.

If the same state and action are passed to a reducer, the same result is always produced because reducers are pure functions. The state is also immutable, which makes it possible to implement difficult tasks like infinite undo and redo. It is also possible to implement time travel — that is, the ability to move back and forth among the previous states and view the results in real time. 💡 Reducers take the previous state of the app and return a new state based on the action passed to it.

What is Redux used for?

This is because React only allows for a uni-directional flow of data. That means data cannot be sent from a child to a parent; it has to flow downward from the parent to the child. This thought model works very well with Redux where we cannot directly modify the state. Instead, we dispatch actions that intend to change the state, and then separately, we observe the resulting state changes.

Now, instead of returning a new object, we are mutating isAddedToCart prop on the state like above. This ensures that neither the views nor the network callbacks will ever write directly to the state. Because all changes are centralized and happen one by one in a strict order, there are no subtle race conditions to watch out for.

What Are Reducers in Redux?

If an action is sent to the store, then the store needs to change the state according to the action. For this, it calls known Reducers, It takes the current state of the application and returns the action that needs to be performed on the state. This makes it easy to create universal apps, as the state from your server can be serialized and hydrated into the client with no extra coding effort. A single state tree also makes it easier to debug or inspect an application; it also enables you to persist your app’s state in development, for a faster development cycle. Some functionality which has been traditionally difficult to implement – Undo/Redo, for example – can suddenly become trivial to implement, if all of your state is stored in a single tree.

This is not just only to show them in the view, but also to manage or update them or perform some logic based on their value. Redux is a pattern and library for managing and updating application state, using events called “actions”. It serves as a centralized store for state what is redux that needs to be used across your entire application, with rules ensuring that the state can only be updated in a predictable fashion. This means it can flow singly only not going to reverse order is possible. Also, it maintains the flow of data in a very efficient manner.

What You’ve Learned​

Redux is an open-source JavaScript library used to manage application state. It was first introduced by Dan Abramov and Andrew Clark in 2015. “Reducer” functions get their name because they’re similar to the kind of callback function you pass to the Array.reduce() method. The Redux DevTools Extension shows a history of the changes to the state in your Redux store over time. This allows you to debug your applications effectively, including using powerful techniques like “time-travel debugging”.

Remember, this data is not needed by the parent component, but because its children need to share data, it has to provide a state. In an app where data is shared among components, it might be confusing to actually know where a state should live. Ideally, the data in a component should live in just one component, so sharing data among sibling components becomes difficult. Redux is an example of a JavaScript library whose enduring popularity is a testament to its value.

Mobile App

As we know that if we have an application that stores something and performs some actions which seem to be changeable we have to make it necessary in the state of the application. For this, we have to perform some actions and this is the only way in Redux. Redux is nothing more than plain JavaScript objects which are holding the information needed for changing the state of the application. In other words, Redux is a pattern-based library that is used to manage and update the application state.