React Native is an open source framework by Facebook for building iOS and Android applications using JavaScript only. It uses the same fundamental UI building blocks as regular iOS and Android. React developers don’t have to build the same app for iOS and Android from scratch. React Native allows developers to reuse the same code for different mobile operating systems with best practices, generators and more.

Features

• Don’t Waste Time Recompiling
  Instead of Recompiling, Hot Reloading enables applications to run the code faster while retaining the application state. It injects edited files that is very useful while tweaking the UI, to keep the app running.
• Understand es6/flow/jsx
  You can use es6 syntax easily if you have a strong grip on the ECMA Script 6 language. React Native contains a tool called Packager that transforms es6/flow/.jsx files into normal JavaScript that the VMware can understand.
• Instantly Reload (Live Reload)
  Rather than constantly reloading changes within the application, you can enable Live Reload in React Native for instant reloading.
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Pros

• It’s Cross-Platform.
• It has a Greater Feedback cycle that saves a lot of development time.
• It allows iterative testing due to its Hot Reload and Live Reload feature.
• Its overall performance is better than other platforms. E.g. Cordova.
• It uses multiple cores simultaneously: JavaScript code runs on one core and app view on the other.
• All user interactions (taps and gestures) are processed by the platform (iOS or Android) and not by JavaScript.
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Cons

• No official IDE is provided by Facebook, therefore, alternatives are used for JavaScript Editor. For example, Atom & Sublime.
• JavaScript has a single dedicated device thread, while native code is free to use whatever threads it wants. In performance, React Native stays behind an optimized native application.
• As React Native is relatively new, it doesn’t have authentic documentation and sample source codes.
• React Native was created for iOS first, so it’s more difficult to use for Android. It doesn’t have additional features