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React Native

React Native​

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  1. What is the difference between React Native and React?​

    React is a JavaScript library, supporting both front end web and being run on the server, for building user interfaces and web applications.

    React Native is a mobile framework that compiles to native app components, allowing you to build native mobile applications (iOS, Android, and Windows) in JavaScript that allows you to use React to build your components, and implements React under the hood.

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  1. How to test React Native apps?​

    React Native can be tested only in mobile simulators like iOS and Android. You can run the app in your mobile using expo app (https://expo.io) Where it syncs using QR code, your mobile and computer should be in same wireless network.

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  1. How to do logging in React Native?​

    You can use console.log, console.warn, etc. As of React Native v0.29 you can simply run the following to see logs in the console:

    $ react-native log-ios
    $ react-native log-android

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  1. How to debug your React Native?​

    Follow the below steps to debug React Native app:

    1. Run your application in the iOS simulator.
    2. Press Command + D and a webpage should open up at http://localhost:8081/debugger-ui.
    3. Enable Pause On Caught Exceptions for a better debugging experience.
    4. Press Command + Option + I to open the Chrome Developer tools, or open it via View -> Developer -> Developer Tools.
    5. You should now be able to debug as you normally would.

React supported libraries & Integration​

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  1. What is reselect and how it works?​

    Reselect is a selector library (for Redux) which uses memoization concept. It was originally written to compute derived data from Redux-like applications state, but it can't be tied to any architecture or library.

    Reselect keeps a copy of the last inputs/outputs of the last call, and recomputes the result only if one of the inputs changes. If the the same inputs are provided twice in a row, Reselect returns the cached output. It's memoization and cache are fully customizable.

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  1. What is Flow?​

    Flow is a static type checker designed to find type errors in JavaScript. Flow types can express much more fine-grained distinctions than traditional type systems. For example, Flow helps you catch errors involving null, unlike most type systems.

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  1. What is the difference between Flow and PropTypes?​

    Flow is a static analysis tool (static checker) which uses a superset of the language, allowing you to add type annotations to all of your code and catch an entire class of bugs at compile time.

    PropTypes is a basic type checker (runtime checker) which has been patched onto React. It can't check anything other than the types of the props being passed to a given component. If you want more flexible typechecking for your entire project Flow/TypeScript are appropriate choices.

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