When other libraries are modifying the DOM, it can quickly become out of sync with what React expects. This could, and more often than not, will, lead to errors when React tries to reconcile changes:.
From here, the component is stable and its lifecycle dormant until one of two things happens. The first thing that could happen is the component's parent could pass it new props. The second is some event or interval triggers a change in internal state. These two actions, of course, necessitate a re-render. Before a re-render happens, there are a few other lifecycle methods that will be called.
The first method called during a property update cycle is componentWillReceiveProps. Here, we not only know that the component is about to receive a new set of properties, but we also can see what those properties are and how they compare to the old ones:.
This lifecycle method is a good place to update state that is somehow derived from props because it is the only update lifecycle method that is not called for both prop and state changes.
This brings us to the next lifecycle method that is called when either props or state are updated: shouldComponentUpdate. This method is unique among lifecycle methods in that it is the only one that expects a return value.
As you may be able to guess, the return value expected is a Boolean. If the method returns true , the lifecycle continues as we expect it.
However, if shouldComponentUpdate returns false , the lifecycle is short-circuited here and a re-render does not occur. Within this method, we can see not only the new properties, but also the new state that will be rendered:. If a component does not define this method, it is always assumed to be true.
React, though, gives you the ability to override this behavior. This can become important in large applications with many components and many layers of component nesting. Using shouldComponentUpdate , we can fine-tune when a component re-renders in order to enhance the performance of our application. This is important because, while React is good at optimizing renders, rendering is still computationally expensive and excessive rendering can slow down an application to the point where a user can feel stuttering.
If shouldComponentUpdate returns true or is not defined by the component , the next step in the lifecycle is componentWillUpdate , which is the last step before re-rendering.
Here, like in shouldComponentUpdate , we have access to both the new properties and the new state:. At this point, React will call render on the component again, getting its new JSX representation.
Once this process is complete, we arrive at the next step of the lifecycle, which is componentDidUpdate. This method is very similar to componentWillUpdate , except that it receives the previous properties and state as arguments:.
Now, we've completed the update lifecycle. At this point, once again the component remains dormant until another change in properties or state occurs. This process continues over and over again until the component is removed, or unmounted, from the DOM.
Just before a component is removed from the DOM, the final stage of the component's lifecycle will be completed. Here, React calls the optional componentWillUnmount method, which receives no arguments. This method is a good place to clean up anything that the component created over the course of its life.
For instance, if the component started an interval upon mounting, here would be a good place to stop that interval.
In our componentWillMount example, we showed starting a countdown interval that fired every second after the component mounted. If we store that interval's ID in state, we can then stop the interval when the component is being unmounted:.
While we've gone through and demonstrated how each lifecycle method might be used within a component, it is important to point out that we would very rarely need to use every component lifecycle method in a single component.
Remember that each one is optional and need not be defined by the component unless some feature of its functionality necessitates it. In fact, our NewsItem component does not need any of these lifecycle methods to do exactly what we want. In React, there are three ways to define a component. The way we've seen so far uses ES classes to define a component and its methods. This is currently the most common method for defining React components and, in fact, the one you'll encounter most often in documentation and in this book.
Before ES and its class syntax became popular and brought into React, the way to define a component was by using the React. This function takes as an argument a JavaScript object that describes the component and its methods. This conceptually is very similar to the way we have seen so far, but has some syntactic differences.
To demonstrate, let's take a look at what our NewsItem component looks like using this method:. Other than the obvious syntactic differences, there are a few subtle differences in how we define and use components with React. The first is instead of simply assigning the state in the class constructor, we define a getInitialState method in the component, which returns the initial component state as an object:. The next thing we might notice is that, previously, event handler functions were bound to the component's this context either in the constructor or within the event attribute assignment.
When using the React. We may have also noticed that rather than defining the propTypes statically on the class, we instead do it within the component object:. This component does not need default properties, but if it did, we would also define those inside the component object. We do this by defining a method similar to getInitialState called getDefaultProps that also returns an object:.
For simple components that maintain no internal state, we can define them simply as functions that take props as input and return JSX elements as output.
These components are not only succinct, but may in the future be more performant than components defined in other ways. For these reasons, it is recommended that we use functional components wherever possible. Because of its simplicity and lack of internal state, our Title component from an earlier section is a good candidate for being a functional component. Here is what that component would look like with this alternate syntax:.
Taking advantage of ES arrow function syntax, our large traditionally defined component has been simplified to a single function. In addition to not having internal state, functional components don't have lifecycle methods. They can, however, have defaultProps and propTypes that can be specified in the same manner as class components:. The React library has created a new way to develop user interfaces for web applications through creating declarative and composable components in the new, but familiar, JSX syntax.
Since its introduction, it has grown immensely in popularity. At Facebook's F8 developer conference in , it was estimated that upwards of , developers were using React in some way. This enthusiasm led the community to look for new places to use their favorite library, and in early , React Native was born.
In this chapter, we covered the fundamentals of React, from conception to implementation. We learned how to take a user interface and structure it as components, the building blocks of React applications. Starting with simple components, such as a static title, we then built up to more complex components by adding props, event handlers, state, and lifecycle methods. Finally, we looked at some alternate ways of representing React components and discussed when each was appropriate. In the next chapter, we will take this knowledge of React into the realm of native mobile applications by building a Hello World application in React Native.
Eric Masiello is a lead software engineer for Vistaprint Digital. Formerly, Eric worked as a principal frontend engineer for the Advisory Board Company and built mobile apps for the Education Advisory Board.
He has taught frontend topics at General Assembly in Washington, D. Jacob Friedmann is a developer living in Seattle, WA. He has been working as a developer professionally for 5 years and is currently a principal software engineer at AddThis, an Oracle company.
At AddThis, he works on large front and backend applications. He has taught several classes, including frontend web development and JavaScript development through General Assembly in Washington D.
Improve your React Native mobile development skills or transition from web development to mobile development with this practical solution-packed guide. About this book React Native has completely revolutionized mobile development by empowering JavaScript developers to build world-class mobile apps that run natively on mobile platforms. Publication date: January Publisher Packt. Branches Tags. Could not load branches. Could not load tags.
Latest commit. Git stats 38 commits. Failed to load latest commit information. View code. Implement React Navigation like a pro Enhance your animation skills by mimicking animations used in several popular applications Understand how notifications work on Android and iOS through React Native Leverage Google Firebase to send remote push notifications Instructions and Navigation Assumed Knowledge To fully benefit from the coverage included in this course, you will need: This course teaches by example and is broken down into digestible chunks.
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Check your mailbox for the verification email from Amazon Kindle. Related Booklists. Post a Review To post a review, please sign in or sign up. If you already have some JavaScript knowledge or are using React on the web, then you will be able to quickly get up and running with React Native for iOS and Android.
What You Will Learn Set up the React Native environment on both devices and emulators Gain an in-depth understanding of how React Native works behind the scenes Write your own custom native UI components Learn the ins and outs of screen navigation Master the art of layout and styles Work with device-exclusive data such as geolocation Develop native modules in Objective-C and Java that interact with JavaScript Test and deploy your application for a production-ready environment In Detail React Native is a game-changing approach to hybrid mobile development.
Web developers can leverage their existing skills to write mobile applications in JavaScript that are truly native without using cross-compilation or web views. These applications have all of the advantages of those written in Objective-C or Java, combined with the rapid development cycle that JavaScript developers are accustomed to. Web developers who want to develop native mobile applications face a high barrier to entry, because they are forced to learn platform-specific languages and frameworks.
Numerous hybrid technologies have tried to simplify this process, but have failed to achieve the performance and appearance that users expect. This book will show you all the advantages of true native development that React Native has without the steep learning curve, leveraging the knowledge you already have.
We do this by getting you up and running quickly with a sample application. Next, we'll introduce you to the fundamentals of creating components and explain how React Native works under the hood.
Once you have established a solid foundation, you will dive headfirst into developing a real-world application from start to finish. Along the way, we will demonstrate how to create multiple screens and navigate between them,use layout and style native UI components, and access native APIs such as local storage and geolocation.
Finally, we tackle the advanced topic of Native modules, which demonstrates that there are truly no limits to what you can do with React Native. Style and approach This book provides a simple and easy way to build mobile applications in JavaScript. Each topic takes you through the life cycle of creating a fully-functional native app, with detailed explanations of the entire process.
Build cross-platform applications of varying complexity for the web, mobile, and VR devices using React tooling Key Features Build React applications at scale using effective React patterns and best practices Explore React features such as Hooks, the Context API, and the Suspense API Extend React's integration with React Native for building cross-platform mobile apps and games Book Description Developed by Facebook, React is a popular library for building impressive user interfaces.
React extends its capabilities to the mobile platform using the React Native framework and integrates with popular web and mobile tools to build scalable applications. React Projects is your guide to learning React development by using modern development patterns and integrating React with powerful web tools such as GraphQL, Expo, and React You'll start building a real-world project right from the first chapter and get hands on with developing scalable applications as you advance to building more complex projects.
Throughout the book, you'll use the latest versions of React and React Native to explore features such as Higher Order Components HOC , Context, and Hooks on multiple platforms, which will help you build full stack web and mobile applications efficiently. Finally, you'll delve into unit testing with Jest to build test-driven apps.
By the end of this React book, you'll have developed the skills necessary to start building scalable React apps across web and mobile platforms. What you will learn Create a wide range of applications using various modern React tools and frameworks Discover how React Hooks modernize state management for React apps Develop progressive web applications using React components Build test-driven React applications using the Jest and Enzyme frameworks Understand full stack development using React, Apollo, and GraphQL Perform server-side rendering using React and React Router Design gestures and animations for a cross-platform game using React Native Who this book is for The book is for JavaScript developers who want to explore React tooling and frameworks for building cross-platform applications.
Basic knowledge of web development, ECMAScript, and React will assist with understanding key concepts covered in this book. Discover the current landscape of full-stack development and how to leverage modern web technologies for building production-ready React.
Together, these technologies, when reinforced with the capabilities of TypeScript, provide a cutting-edge stack for complete web application development. This book takes a hands-on approach to implementing modern web technologies and the associated methodologies for building full-stack apps. You'll begin by gaining a strong understanding of TypeScript and how to use it to build high-quality web apps. Next, you'll get to grips with server-side development with Express, including authentication with Redis-based sessions and accessing databases with TypeORM.
The book will then show you how to use Apollo GraphQL to build web services for your full-stack app. By the end of this book, you'll be able to build and deploy complete high-performance web applications using React, Node, and GraphQL.
A good understanding of JavaScript programming is required before getting started with this web development book. TypeScript is among the fastest-growing languages, helping developers build full-stack apps by integrating with powerful frameworks such as React and Node.
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