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How To Install and Setup React Native on Mac

React Native Development Environment Installation:With the rapid growth of online websites, businesses, and the general ecosystem, it is crucial that website UIs load quickly on smartphones to encourage smartphone-based internet consumption. Facebook developed React Native from a need to generate UI elements efficiently, which formed the basis for creating the open-source web framework. Its native cross-platform capabilities allow usage for a wide range of platforms for application development, including Android, Web, Windows, UWP, tvOS, macOS, iOS, and AndroidTV. Microsoft also released a preview release in May 2020 that expanded the range of the React Native world, allowing desktop app development. React Native runs in the background of the destination device, and then communicates with the native platform via a batched asynchronous bridge. Its three main advantages are:It allows faster development due to its native natureThough it has a syntax styling similar to CSS or HTML, it is much quicker and efficientIt is flexible as it allows developers to write native code in various languages, including Java, Kotlin, and Swift.This article is about how to install and configure React Native CLI environment. First, we will learn how to install the framework, then check whether it works well and finally develop an app.PrerequisitesBasic computer proficiencyAn account with Administrative privileges on your computerAccess to the outlined documents and softwareA working internet connection to download the installation filesAudienceThis article guides first-time React Native users, junior developers, and developers with no experience with React Native. If curiosity nudged you to learn the framework due to the hype around React, then this is the guide you need.System requirementsSoftwareXcode version 11.3.1 or newer is required. Nodejs version 12 LTS or newer is required.HardwareMacOS requires a Mac device to operateRam - 4GBStorage - 10GBThese requirements ensure your tools run quickly and have enough storage for installation and development.System RequirementsReact Native requires macOS High Sierra (10.13) or higher to run efficiently.Installation through HomeBrew:HomeBrew is a package manager that helps you install and manage packages on Mac, and thus it will be essential to our installation process. You will install HomeBrew so that you can use it to install all the other tools necessary for React Native environment, including Nodejs, git, Watchman, and JDK.First download HomeBrew using the above link, then execute the command below in the Command Line Interface:brew—versionThe command verifies whether HomeBrew has been successfully installed and outputs the specific version installed as the following result shows:homebrew 2.1.7 homebrew/homebrew-core (git revision f487; last commit 2020-05-26)When the version is unavailable, you can install HomeBrew via this code:/usr/bin/ruby -e “$(curl –fsSL https://raw.githubusercontent.com/HomeBrew/install/master/install)”After installation, check whether HomeBrew has installed properly using the following command:brew--versionIf the software is well installed, the result will show the version and date as shown:homebrew 2.1.7 homebrew/homebrew-core(git revision f487; last commit 2020-05-26)NodejsReact Native is a JavaScript platform; hence it needs Nodejs to provide a JavaScript runtime.  Nodejs also provides essential tools such as a local webserver with live reloading, network tools, command-line tools, and web APIs.Use the HomeBrew command below to install Nodejs:brew install nodeCheck whether the installation is successful through the following command:node—versionIf the installation has occurred successfully, the Nodejs version will show up:V12.6.0Installation of Nodejs also includes installation of npm, the Node Package Manager. It would help if you had npm to help you install packages, libraries, and vital tools for your React development environment. To verify if npm is successfully installed, execute the following command:npm—versionIf the installation is successful, you will see the version as shown below:6.9.0WatchmanWatchman monitors the files and folders utilized by the framework and triggers specific actions if the files are modified. It would be best if you had Watchman for React Native to monitor source codes and rebuild them once they are changed.To install Watchman, execute the command below:brew install watchmanVerify installation through:watchman --versionif properly installed, the result will show the version as shown below:4.9.0React Native CLIYou need React Native CLI to develop the app by react-native. React Native CLI is installed by executing the npm command below:npm install --g react-native-cliCheck if the installation is successful using the following command:react-native --versionSometimes, users may get an error when using the npm install --g react -native-cli command. To avoid this, try entering sudo before this command, then enter your system password.If the installation is successful, you will see the version as shown:react-native-cli:2.0.1 react-native:n/a - not inside a React Native ProjectXcodeYou need Xcode for iOS app development, and you can download it via the above link. After installation, configure the Command Line Tools. Execute Xcode and go toXcode > Preferences > LocationsYou should see the Command Line Tools settings showing the version of Xcode as:Xcode 10.2.1 (10E1001)If the settings do not look like that, select the last version of the Command Line Tool from the dropdown menu.Go to components and select an iOS emulator, then download it (this is for those without iOS devices to run and test their apps on. It is also easier than using an actual device.)Move account tabs, select apple id, and input your apple id.Open Xcode and create a new project, name it anything, then close it. After project creation, click the root file and select "sign in and capabilities," then select your user id. Select your emulator and keep it ready for development.CocoapodsCoacoapods manages dependencies in iOS development, and thus it is necessary to develop an app by react-native.Install Cocoapods through the following command:sudo gem install cocoapodsVerify installation through:pod --versionif installation is successful, you can see the version as shown below:1.7.5JDKThe Java Development Kit is essential for the development of Android apps with react-native. Install JDK through the command below:brew tap AdoptOpenJDK/openjdk brew cask install adoptopenjdk8Verify installation through:java -versionIf you see the Java version as shown below, then Java has been successfully installed:openjdk version "1.8.0_222" OpenJDK Runtime Environment (AdoptOpenJDK)(BUILD 1.8.0_222-b10) OpenJDK 64-Bit Server VM (AdoptOpenJDK)(build 25.222-b10, mixed mode)JDK Installation also installs the Java Compiler, which can be verified by executing the following command:javac -versionIf the installation is successful, the following result shows up:javac 1.8.0_222Android StudioAndroid Studio is also an essential tool for developing an Android app using react-native.CONFIGURATIONOn the install type screen, select the custom option, choose your preferred theme, then select the performance (Intel R HAXM) option and Android Virtual Device option. Click Next, then leave the Emulator settings as they are, and click next again. Allow the standard installation to continue and click Finish to complete the process.ANDROID STUDIO SDK CONFIGURATIONClick Configure>SDK Manager and proceed to Android SDK Configuration.Select the Show Package Details option and select the following options:Android SDK Platform 28Intel  X86 Atom System ImageGoogle APIs Intel x86 Atom System ImageGoogle APIs Intel x86 Atom_64 System ImageClick ok to install the options selected.In the SDK Tools Window, select show package details >Android SDK Build Tools >Android SDK Build Tools 23.0.1.ANDROID STUDIO ENVIRONMENT VARIABLE CONFIGURATIONYou need to set environment variables to ensure the development environment fits your specifications.  Ensure that the ANDROID_HOME environment variable connects to your existing Android SDK to avoid complications.Open and include the following code to the ~/.bash_profile file or the ~/.zshrc file to add the environment variables:For .bash_profile users, use the following command:source ~/.bash_profileAfter configuration, restart the terminal, then execute the following command: adbThe correct result if all variables are successfully configured is:Android Debug Bridge Version 1.0.41 version 29.0.1-5644136 Installed as /Your Android SDK Directory Location/platform-tools/adbGit1.You can also use git, which comes with Xcode. However, if its unavailable, run the code below:brew install gitgit is a substitute for the Android Studio development environment.Gradle DaemonSometimes you may need to modify the java code, in which case, your development speed will be affected. Gradle Daemon is a tool that manages these changes to speed up your development.Other Installation MethodsExpo CLIExpo CLI is a tool built to install and manage react-native frameworks. However, its unsuitable feature is that it has numerous native features, which makes building an app tedious and also makes the app size more extensive than it needs to be. Additionally, incorporating elements in an app that are not available in Expo CLI is difficult, making the tool unsuitable for developers. Despite that, Expo CLI has many useful native tools, unlike React Native CLI, such as geolocation, camera, the microphone that can come in handy for most application needs. Expo CLI is a much easier route than the react-native CLI route.The installation process is as follows:1.Install the Expo CLI command line utility using:Npm install –g expo-cli2.Run the command below to create your first project:expo init my app3. Browse to the directory with the following command in the terminal:4. Finally, run the projectExpo start5. A development environment server will be started by these commands. Running the app requires installing the Expo client app to your device (iOS/Android) then connecting it to your computer. Android requires scanning the QR code on the terminal to authenticate the project, while iOS requires QR code scanning using the camera app. On the Android (emulator/real device), use the following command to initialize the app:npm run android6. While on the iOS emulator run:npm run iosExpo has docs that you can reference for solutions or even utilize the Expo Forums created for the Expo community to ask questions.Expo is mostly best suited for beginners as it does not include the use of native code thus cannot be used to develop complex applications with custom components.TestingProject structureReact Native project structure consists of a project directory with configuration files such as package.json, app.json, .watchman.json at the root; separate Android and iOS folders; a _tests_ folder with validation tests for the project; a nodes_module for housing smaller app modules; and an index.js file that maps the application and serves as the initialization point of the application. package.json  specifies project dependencies and versions, while app.json contains the app name.The npm (node package manager) manages the node_modules folder, which stores all the project library dependencies. You should avoid modifying the files present in the folder since alterations performed cannot be assured to be stable from updates/installs. Assets in the public folder are to be shared publicly. The src folder contains all development work by the developer, including components and source codes.Developing an app1. First, you need to lock the version you build with to ensure the app still works even after updates, using the following command:npm config set save-exact=true2. Create a native project through the command:react-native init AwesomeProject cd AwesomeProject react-native run-iosYour new app will run successfully in the emulator.3. In iOS, execute the command below:cd SampleApp #react-native run ios npm run iosThe react-native app will show up on the emulator.4. On Android, run the following command:cd SampleApp #react-native run-android npm run androidYour Android emulator will output:Welcome to ReactSecond App VerificationHello World is a simple program for most development environments. Open index.ios.js for iOS or index.android.js for Android, then proceed to delete everything between the tags <View></View>.  Write <Text>Hello World</Text> and execute the emulator.The result will be Hello World on the screen.Modifying Your AppAfter successful testing, you can modify your app through the following steps:Open index.ios.js or index.android.js and edit some files.Click CommandX + R in the iOS Emulator and reload to see changes.Potential issuesYou might encounter problems while installing Cocoapods or React Native CLI - the most probable solution is entering a sudo command before the installation command, which will prompt you for your system password. Input the password, and your installation will go through just fine. You might also get this result [Broken AVD system path. Check your ANDROID_SDK_ROOT value]. Check if you installed android -sdk using homebrew; if you did, then uninstall it through the following command: brew uninstall android-sdk Another error is No ANDROID_HOME which means the bash files do not point to the ANDROID_HOME path. You can correct this through the following steps:Open and add the following code to the ~/.bash_profile file or the ~/.zshrc file to add the environment variables:#export ANDROID_HOME=$HOME/Library/Android/sdk export ANDROID_HOME=android SDK directory location/ Android/sdk export PATH=$PATH:$ANDROID_HOME/emulator export PATH=$PATH:ANDROID_HOME/tools export PATH=$PATH:$ANDROID_HOME/tools/bin export PATH=$PATH:$ANDROID_HOME/platform-toolsFor .bash_profile users, use the following command:source ~/.bash_profileThen proceed to verify the correction using the following code:echo $ANDROID_HOME // default: /Users/<USERNAME>/Library/Android/sdkAndroid Emulator won't run from Android Virtual Device Manager – Android Studio rarely shows an error that may occur in the Android Device Emulator; thus, you need to utilize the command line and run the commands below to check the name of the Android virtual device:Avdmanager list avdThen runEmulator –avd <NAME>Wait for the device to boot up, then run your app in the emulatorReact-native run-androidYour app should run successfully.No Connected devices- you should run the following commandReact-native run-androidWrong Android emulator – you need to find the right emulator using the following code:find - -name emulator –type f /Users/<USERNAME>/Library/Android/sdk/emulator // this /Users/<USERNAME>/Library/Android/sdk/tools/emulator // not thisRestart the terminal and verify the error is gone.Avdmanager not found- write ~/.bash_profile, then add the following code afterwards:PATH=$PATH:$ANDROID_HOME/tool s/bin export PATHthen runsource ~/.bash_profileQuit and restart the terminal, then run the tools.Uninstallation procedureSometimes you might need to uninstall and wipe off the whole react-native environment due to issues such as a broken development environment which can be caused by misusing commands or assigning storage to variables incorrectly.  To do so efficiently, use the uninstall command together with the -g flag, then include the scope if the package is scoped.  A good example is as follows;npm uninstall -g react-native-cliornpm uninstall <package_name>for scoped package usenpm uninstall <@scope/package_name>As our installations have a package.json file, you might need to remove a package from the dependencies in that file. Use the following commands to effect these changes:npm uninstall --save <package_name>or the following for a scoped packagenpm uninstall --save <@scope/package_name>You will also need to verify if the uninstallation is successful through the following commands on macOS:ls node_modulesThis command ensures the node_modules do not contain a folder for the uninstalled files.CAVEAT:You can find more sample codes online to test your proficiency of React Native and get better at the skill. React Native is based on MIT License that grants Facebook copyright for portions of React Native for macOS extension derived from React Native. Remember to only download software from the official stated sites to avoid downloading compromised, malware-ridden software that can cripple your computer. If your computer shows any warning while executing any of the above steps, ensure to verify the software, ask an expert or ask on online community platforms. After completing and understanding all these steps successfully, you are now officially a beginner. You can proceed to the next stages of React Native app development until you become an expert. Some of the most significant areas you need to look at afterwards include animation, command-line instructions, components, shareable APKs, custom fonts, debugging, ESLint, images, layout, HTTP requests, Firebase integration, listview, native modules, and routing.The guide presented has shown how to install React Native through various methods and why the tools stated are required, then showed examples of apps and finally the uninstallation procedure. Tooling and development in React Native are simple, and the learning curve is short, making it an ideal framework for web developers.  The growth of internet consumers, cross-platform development, and the whole of the internet ecosystem is an excellent catalyst for React Native to grow in popularity among developers. It offers them faster development speed while offering internet consumers speedier loading times and more beautiful website UIs.  As you have seen, React development is simple; hence it should convince you to get started and launch your own apps within a short period. Being a new but highly applicable language, React Native holds a lot of opportunities, career wise and development wise. There are also numerous React Native platforms on the internet that can help you solve challenges you might face in development. Keep coding and have fun!

How To Install and Setup React Native on Mac

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How To Install and Setup React Native on Mac

React Native Development Environment Installation:

With the rapid growth of online websites, businesses, and the general ecosystem, it is crucial that website UIs load quickly on smartphones to encourage smartphone-based internet consumption. Facebook developed React Native from a need to generate UI elements efficiently, which formed the basis for creating the open-source web framework. Its native cross-platform capabilities allow usage for a wide range of platforms for application development, including Android, Web, Windows, UWP, tvOS, macOS, iOS, and AndroidTV. Microsoft also released a preview release in May 2020 that expanded the range of the React Native world, allowing desktop app development. React Native runs in the background of the destination device, and then communicates with the native platform via a batched asynchronous bridge. Its three main advantages are:

  • It allows faster development due to its native nature
  • Though it has a syntax styling similar to CSS or HTML, it is much quicker and efficient
  • It is flexible as it allows developers to write native code in various languages, including Java, Kotlin, and Swift.

This article is about how to install and configure React Native CLI environment.
First, we will learn how to install the framework, then check whether it works well and finally develop an app.

Prerequisites

  • Basic computer proficiency
  • An account with Administrative privileges on your computer
  • Access to the outlined documents and software
  • A working internet connection to download the installation files

Audience

This article guides first-time React Native users, junior developers, and developers with no experience with React Native. If curiosity nudged you to learn the framework due to the hype around React, then this is the guide you need.

System requirements

Software

  • Xcode version 11.3.1 or newer is required. 
  • Nodejs version 12 LTS or newer is required.

Hardware

  • MacOS requires a Mac device to operate
  • Ram - 4GB
  • Storage - 10GB

These requirements ensure your tools run quickly and have enough storage for installation and development.

System Requirements

React Native requires macOS High Sierra (10.13) or higher to run efficiently.

Installation through HomeBrew:

HomeBrew is a package manager that helps you install and manage packages on Mac, and thus it will be essential to our installation process. You will install HomeBrew so that you can use it to install all the other tools necessary for React Native environment, including Nodejs, git, Watchman, and JDK.

  • First download HomeBrew using the above link, then execute the command below in the Command Line Interface:
brew—version

The command verifies whether HomeBrew has been successfully installed and outputs the specific version installed as the following result shows:

homebrew 2.1.7
homebrew/homebrew-core (git revision f487; last commit 2020-05-26)
  • When the version is unavailable, you can install HomeBrew via this code:
/usr/bin/ruby -e “$(curl –fsSL 
https://raw.githubusercontent.com/HomeBrew/install/master/install)”
  • After installation, check whether HomeBrew has installed properly using the following command:
brew--version

If the software is well installed, the result will show the version and date as shown:

homebrew 2.1.7
homebrew/homebrew-core(git revision f487; last commit 2020-05-26)

Nodejs

React Native is a JavaScript platform; hence it needs Nodejs to provide a JavaScript runtime.  Nodejs also provides essential tools such as a local webserver with live reloading, network tools, command-line tools, and web APIs.

  • Use the HomeBrew command below to install Nodejs:
brew install node
  • Check whether the installation is successful through the following command:
node—version

If the installation has occurred successfully, the Nodejs version will show up:

V12.6.0
  • Installation of Nodejs also includes installation of npm, the Node Package Manager. It would help if you had npm to help you install packages, libraries, and vital tools for your React development environment. To verify if npm is successfully installed, execute the following command:
npm—version

If the installation is successful, you will see the version as shown below:

6.9.0

How To Install and Setup React Native on Mac

How To Install and Setup React Native on Mac

Watchman

Watchman monitors the files and folders utilized by the framework and triggers specific actions if the files are modified. It would be best if you had Watchman for React Native to monitor source codes and rebuild them once they are changed.

  • To install Watchman, execute the command below:
brew install watchman
  • Verify installation through:
watchman --version

if properly installed, the result will show the version as shown below:

4.9.0

React Native CLI

  • You need React Native CLI to develop the app by react-native. React Native CLI is installed by executing the npm command below:
npm install --g react-native-cli
  • Check if the installation is successful using the following command:
react-native --version
  • Sometimes, users may get an error when using the npm install --g react -native-cli command. To avoid this, try entering sudo before this command, then enter your system password.

If the installation is successful, you will see the version as shown:

react-native-cli:2.0.1
react-native:n/a - not inside a React Native Project

Xcode

  • You need Xcode for iOS app development, and you can download it via the above link. After installation, configure the Command Line Tools. Execute Xcode and go to
Xcode > Preferences > Locations

You should see the Command Line Tools settings showing the version of Xcode as:

Xcode 10.2.1 (10E1001)

How To Install and Setup React Native on Mac

  • If the settings do not look like that, select the last version of the Command Line Tool from the dropdown menu.
  • Go to components and select an iOS emulator, then download it (this is for those without iOS devices to run and test their apps on. It is also easier than using an actual device.)
  • Move account tabs, select apple id, and input your apple id.
  • Open Xcode and create a new project, name it anything, then close it. After project creation, click the root file and select "sign in and capabilities," then select your user id. Select your emulator and keep it ready for development.

Cocoapods

Coacoapods manages dependencies in iOS development, and thus it is necessary to develop an app by react-native.

  • Install Cocoapods through the following command:
sudo gem install cocoapods
  • Verify installation through:
pod --version

if installation is successful, you can see the version as shown below:

1.7.5

JDK

  • The Java Development Kit is essential for the development of Android apps with react-native. Install JDK through the command below:
brew tap AdoptOpenJDK/openjdk
brew cask install adoptopenjdk8
  • Verify installation through:
java -version

If you see the Java version as shown below, then Java has been successfully installed:

openjdk version "1.8.0_222"
OpenJDK Runtime Environment (AdoptOpenJDK)(BUILD 1.8.0_222-b10)
OpenJDK 64-Bit Server VM (AdoptOpenJDK)(build 25.222-b10, mixed mode)
  • JDK Installation also installs the Java Compiler, which can be verified by executing the following command:
javac -version

If the installation is successful, the following result shows up:

javac 1.8.0_222

Android Studio

Android Studio is also an essential tool for developing an Android app using react-native.

CONFIGURATION

  • On the install type screen, select the custom option, choose your preferred theme, then select the performance (Intel R HAXM) option and Android Virtual Device option. Click Next, then leave the Emulator settings as they are, and click next again. Allow the standard installation to continue and click Finish to complete the process.

Android Studio

Android Studio

ANDROID STUDIO SDK CONFIGURATION

  • Click Configure>SDK Manager and proceed to Android SDK Configuration.

Select the Show Package Details option and select the following options:

  • Android SDK Platform 28
  • Intel  X86 Atom System Image
  • Google APIs Intel x86 Atom System Image
  • Google APIs Intel x86 Atom_64 System Image
  • Click ok to install the options selected.

How To Install and Setup React Native on Mac

  • In the SDK Tools Window, select show package details >Android SDK Build Tools >Android SDK Build Tools 23.0.1.

ANDROID STUDIO ENVIRONMENT VARIABLE CONFIGURATION

You need to set environment variables to ensure the development environment fits your specifications.  Ensure that the ANDROID_HOME environment variable connects to your existing Android SDK to avoid complications.
Open and include the following code to the ~/.bash_profile file or the ~/.zshrc file to add the environment variables:

Android Studio

Android Studio

For .bash_profile users, use the following command:

source ~/.bash_profile
  • After configuration, restart the terminal, then execute the following command: adb

The correct result if all variables are successfully configured is:

Android Debug Bridge Version 1.0.41
version 29.0.1-5644136
Installed as /Your Android SDK Directory Location/platform-tools/adb

Git

1.You can also use git, which comes with Xcode. However, if its unavailable, run the code below:

brew install git

git is a substitute for the Android Studio development environment.

Gradle Daemon

Sometimes you may need to modify the java code, in which case, your development speed will be affected. Gradle Daemon is a tool that manages these changes to speed up your development.

Other Installation Methods

Expo CLI

Expo CLI is a tool built to install and manage react-native frameworks. However, its unsuitable feature is that it has numerous native features, which makes building an app tedious and also makes the app size more extensive than it needs to be. Additionally, incorporating elements in an app that are not available in Expo CLI is difficult, making the tool unsuitable for developers. Despite that, Expo CLI has many useful native tools, unlike React Native CLI, such as geolocation, camera, the microphone that can come in handy for most application needs. Expo CLI is a much easier route than the react-native CLI route.

The installation process is as follows:

1.Install the Expo CLI command line utility using:

Npm install –g expo-cli

2.Run the command below to create your first project:

expo init my app

3. Browse to the directory with the following command in the terminal:

4. Finally, run the project

Expo start

5. A development environment server will be started by these commands. Running the app requires installing the Expo client app to your device (iOS/Android) then connecting it to your computer. Android requires scanning the QR code on the terminal to authenticate the project, while iOS requires QR code scanning using the camera app. On the Android (emulator/real device), use the following command to initialize the app:

npm run android

6. While on the iOS emulator run:

npm run ios

Expo has docs that you can reference for solutions or even utilize the Expo Forums created for the Expo community to ask questions.
Expo is mostly best suited for beginners as it does not include the use of native code thus cannot be used to develop complex applications with custom components.

Testing

Project structure

React Native project structure consists of a project directory with configuration files such as package.json, app.json, .watchman.json at the root; separate Android and iOS folders; a _tests_ folder with validation tests for the project; a nodes_module for housing smaller app modules; and an index.js file that maps the application and serves as the initialization point of the application. package.json  specifies project dependencies and versions, while app.json contains the app name.

The npm (node package manager) manages the node_modules folder, which stores all the project library dependencies. You should avoid modifying the files present in the folder since alterations performed cannot be assured to be stable from updates/installs. Assets in the public folder are to be shared publicly. The src folder contains all development work by the developer, including components and source codes.

Android Studio

Developing an app

1. First, you need to lock the version you build with to ensure the app still works even after updates, using the following command:

npm config set save-exact=true

2. Create a native project through the command:

react-native init AwesomeProject
cd AwesomeProject
react-native run-ios

Your new app will run successfully in the emulator.

3. In iOS, execute the command below:

cd SampleApp
#react-native run ios
npm run ios

The react-native app will show up on the emulator.

4. On Android, run the following command:

cd SampleApp
#react-native run-android
npm run android

Your Android emulator will output:

Welcome to React

Second App Verification

Hello World is a simple program for most development environments. Open index.ios.js for iOS or index.android.js for Android, then proceed to delete everything between the tags <View></View>.  Write <Text>Hello World</Text> and execute the emulator.

The result will be Hello World on the screen.

Modifying Your App

  • After successful testing, you can modify your app through the following steps:
  • Open index.ios.js or index.android.js and edit some files.
  • Click CommandX + R in the iOS Emulator and reload to see changes.

Potential issues

  • You might encounter problems while installing Cocoapods or React Native CLI - the most probable solution is entering a sudo command before the installation command, which will prompt you for your system password. Input the password, and your installation will go through just fine. 
  • You might also get this result [Broken AVD system path. Check your ANDROID_SDK_ROOT value]. Check if you installed android -sdk using homebrew; if you did, then uninstall it through the following command: brew uninstall android-sdk 
  • Another error is No ANDROID_HOME which means the bash files do not point to the ANDROID_HOME path. You can correct this through the following steps:

Open and add the following code to the ~/.bash_profile file or the ~/.zshrc file to add the environment variables:

#export ANDROID_HOME=$HOME/Library/Android/sdk
export ANDROID_HOME=android SDK directory location/ Android/sdk
export PATH=$PATH:$ANDROID_HOME/emulator
export PATH=$PATH:ANDROID_HOME/tools
export PATH=$PATH:$ANDROID_HOME/tools/bin
export PATH=$PATH:$ANDROID_HOME/platform-tools

For .bash_profile users, use the following command:

source ~/.bash_profile

Then proceed to verify the correction using the following code:

echo $ANDROID_HOME //
default:
/Users/<USERNAME>/Library/Android/sdk
  • Android Emulator won't run from Android Virtual Device Manager – Android Studio rarely shows an error that may occur in the Android Device Emulator; thus, you need to utilize the command line and run the commands below to check the name of the Android virtual device:
Avdmanager list avd

Then run

Emulator –avd <NAME>

Wait for the device to boot up, then run your app in the emulator

React-native run-android

Your app should run successfully.

  • No Connected devices- you should run the following command
React-native run-android

Wrong Android emulator – you need to find the right emulator using the following code:

find - -name emulator –type f
/Users/<USERNAME>/Library/Android/sdk/emulator //
this
/Users/<USERNAME>/Library/Android/sdk/tools/emulator //
not this

Restart the terminal and verify the error is gone.
Avdmanager not found- write ~/.bash_profile, then add the following code afterwards:

PATH=$PATH:$ANDROID_HOME/tool
s/bin
export PATH

then run

source ~/.bash_profile

Quit and restart the terminal, then run the tools.

Uninstallation procedure

Sometimes you might need to uninstall and wipe off the whole react-native environment due to issues such as a broken development environment which can be caused by misusing commands or assigning storage to variables incorrectly.  

To do so efficiently, use the uninstall command together with the -g flag, then include the scope if the package is scoped.  A good example is as follows;

npm uninstall -g react-native-cli

or

npm uninstall <package_name>

for scoped package use

npm uninstall <@scope/package_name>

As our installations have a package.json file, you might need to remove a package from the dependencies in that file. Use the following commands to effect these changes:

npm uninstall --save <package_name>

or the following for a scoped package

npm uninstall --save <@scope/package_name>

You will also need to verify if the uninstallation is successful through the following commands on macOS:

ls node_modules

This command ensures the node_modules do not contain a folder for the uninstalled files.

CAVEAT:

  • You can find more sample codes online to test your proficiency of React Native and get better at the skill. 
  • React Native is based on MIT License that grants Facebook copyright for portions of React Native for macOS extension derived from React Native. 
  • Remember to only download software from the official stated sites to avoid downloading compromised, malware-ridden software that can cripple your computer. If your computer shows any warning while executing any of the above steps, ensure to verify the software, ask an expert or ask on online community platforms. 
  • After completing and understanding all these steps successfully, you are now officially a beginner. You can proceed to the next stages of React Native app development until you become an expert. Some of the most significant areas you need to look at afterwards include animation, command-line instructions, components, shareable APKs, custom fonts, debugging, ESLint, images, layout, HTTP requests, Firebase integration, listview, native modules, and routing.

The guide presented has shown how to install React Native through various methods and why the tools stated are required, then showed examples of apps and finally the uninstallation procedure. Tooling and development in React Native are simple, and the learning curve is short, making it an ideal framework for web developers.  

The growth of internet consumers, cross-platform development, and the whole of the internet ecosystem is an excellent catalyst for React Native to grow in popularity among developers. It offers them faster development speed while offering internet consumers speedier loading times and more beautiful website UIs.  

As you have seen, React development is simple; hence it should convince you to get started and launch your own apps within a short period. Being a new but highly applicable language, React Native holds a lot of opportunities, career wise and development wise. There are also numerous React Native platforms on the internet that can help you solve challenges you might face in development. Keep coding and have fun!

Rajesh

Rajesh Bhagia

Blog Author

Rajesh Bhagia is experienced campaigner in Lamp technologies and has 10 years of experience in Project Management. He has worked in Multinational companies and has handled small to very complex projects single-handedly. He started his career as Junior Programmer and has evolved in different positions including Project Manager of Projects in E-commerce Portals. Currently, he is handling one of the largest project in E-commerce Domain in MNC company which deals in nearly 9.5 million SKU's.

In his role as Project Manager at MNC company, Rajesh fosters an environment of teamwork and ensures that strategy is clearly defined while overseeing performance and maintaining morale. His strong communication and client service skills enhance his process-driven management philosophy.

Rajesh is a certified Zend Professional and has developed a flair for implementing PMP Knowledge Areas in daily work schedules. He has well understood the importance of these process and considers that using the knowledge Areas efficiently and correctly can turn projects to success. He also writes articles/blogs on Technology and Management

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Angular: Add service to module Code Example

What are services in an Angular app?Services is a general term broadly categorized as values, functions, or features that our application may need. Services are made to reuse codes designed for a purpose.Angular services differentiate an element from its service so that the services can be re-used. This increases the modularity of the Angular application. Service in an Angular App can be almost anything, it can be an element, a component, or it can be a module used for some specific purpose.All services in Angular App are classes with a definite purpose. It serves a purpose and serves it well.Some of the very well-known services include:Logging Service: Used for logging in, logging out.Data Fetching: Fetching Data and representing it in a formatted way.Data Service: Fetching and receiving Data.Message Bus: Used for communicating through a set of shared interfaces.Tax Calculator: Calculating Tax by synchronizing with the current Law system.EMI calculator: Easy Monthly Instalment Calculator, mainly used in calculations related to Loan. Application Configuration: Common configuration throughout the application support.ReusabilityReusability is very important when building large-scale applications. Classes built for a common purpose should not be required to be built again and again. This even causes misinterpretation of certain important classes. We need to implement separation of concerns to segregate different classes used for different purposes. This can be achieved by Angular services.In Angular 13 Framework, the services are those objects that get instantiated a maximum of one time during the entire lifetime of any Angular application or Angular module.All the Angular Services contain many methods that maintain data throughout the lifetime of an application. Thus, it has become a medium to share various responsibilities within one or multiple components.Services and Dependency InjectionServices provide us with injectable features. The Angular App provides us the decorator @Injectable for creating a service. 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You can download it fromhttps://nodejs.org/en/download/The latest Version is : node-v16.13.1-x64Install node.js once downloaded:Once you have installed Node.js on your system, open node.js command prompt.To check your version, run node -v in a terminal/console window.Step 2: Use npm to Install Angular CLIUse the following command to install Angular CLInpm install -g @angular/cli Ornpm install -g @angular/cli@latestOrJust go to Angular CLI official website https://cli.angular.io/You will see the whole cli command to create an Angular app. You need to run the first command to install Angular CLI. These steps are same for Windows and Mac.To check Node and Angular CLI version, use ng --version command.Step 3: Create an app called ngApp4ServiceSyntax:ng new app_nameC:\>ng new ngApp4Service It asks forWould you like to add Angular routing? 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Create GraphQL API with example

Recently, GraphQL has made a lot of buzz among the developer community, and it has been receiving a lot of attention because of its dynamic nature along with its capability to fetch data, which is a lot less redundant. In this Code Tutorial, you will get to learn about what GraphQL really is, why has it created such hype amongst new-age developers, how is it different from the REST approach, and finally you will be building our own API with GraphQL along with Code Tutorials. Let’s get started!What is GraphQL? A quick primerBefore understanding what GraphQL is, let’s first understand what Query Languages are. Query Languages are computer languages that request the data from a database (called queries) to a client-side application through a server. A well-known example is Structured Query Language or SQL.Coming to GraphQL, by definition - “GraphQL is an open-source data query and manipulation language for APIs, and a runtime for fulfilling queries with existing data” (source: Wikipedia). Simply put, GraphQL is a new age Query Language developed by Facebook in 2012 that helps Application Programming Interfaces (APIs) fetch only that data which is requested by the client, and nothing else. This enormously reduces the redundant data at the API endpoint and making the requests blazing fast and developer friendly.Initially, GraphQL was an internal project of Facebook and it was created for fetching specific data and reducing network usage. In 2015, it was released publicly at the React.js conference and reference implementations and specifications of GraphQL in JavaScript were open-sourced. Later most of the programming languages adopted that. New languages like Python, Node.js, Java, C#, PHP, GO, and many more, support GraphQL.But wasn’t the same thing already being done by RESTful APIs? The answer is yes, but GraphQL is different than REST in a lot of ways.GraphQL is Client-Driven, whereas REST is Server-Driven.Queries are organized in terms of Schema and strict typecasting in GraphQL, whereas REST has Endpoints for that task.GraphQL calls Specific data with a single call. REST calls Fixed data with multiple calls.Instead of the GET, POST, PUT, DELETE operations in REST, GraphQL has Query, Mutation, and Subscription for data manipulation.Some of the other advantages of using GraphQL are:GraphQL is faster than other communication APIs.GraphQL can retreat multiple resources and results with a single request.It is easy to use complex systems and microservices with GraphQL as it unifies and hides their complexity.It offers multiple libraries and powerful tools for various projects such as GraphiQL, GraphQL Explorer, Apollo.No under and over data fetching. It fetches the amount of data that is required.The core building block of GraphQL is its schema which is used as a middle way between server and client while defining the accessibility of the data.  A GraphQL schema is written in Schema Definition Language (SDL) and refers to the exact mutations and queries that a client can execute against your data graph. It can be built with any programming language. Simply, the schema defines the type of data that can be fetched, the relationships between these types of data, and what type of queries are allowed. The most basic components of a GraphQL schema are object types. They represent a kind of object you can fetch from your service along with the fields it has. Further, schema helps the client validate their query and eliminate unavailable data or the wrong structure stage.The other two fundamental parts of GraphQL are Query and Resolver. The request to fetch a particular data is called a query and a resolver is used to tell the server from where and how to fetch the data corresponding to the given field. You can execute the GraphQL queries either by Command line or by using a GraphQL server.GraphQL works in three parts – a query to read data, a mutation to write data, and a subscription to receive real-time data over time.Now that you know the ‘What’ and ‘Where’of GraphQL, let’s dive straight into our favorite part, the development phase.Let’s Play with GraphQLTo get started with GraphQL, you need a server that serves your API and a client that connects to your service endpoints. In this section, you will learn about a step-by-step procedure of building an API using GraphQL and Express on top of Node.js. In the next section, you will be implementing these prerequisites into code and start our development for the API.Prerequisites:Understanding of GraphQLNode Package Manager (or NPM) with version 10+Knowledge of basic querying and server-side programming.We will be needing a database to store the user data and everything else that a client-side application can request for. For this, you will be using LowDB, which is a simple file based JSON database for small projects in the localhost. Then you will be needing middleware to connect our database system to the requesting frontend application. For this, you will be using the Express middleware with the GraphQL implementation of Express - the Graphql-express library. Finally, you will be making a client-side application using react which can request all the data from the local database and can perform operations on the database like read, write, and delete.So, our roadmap is simple and straightforward. Create a Database Schema > Use a middleware server to query the database > Create a frontend application to use the data. If this is too much at once for you, do not worry as this is article is being written keeping in mind that the reader is a first-timer for GraphQL and basic querying as usual. Now, let’s dive into the code.Setting up Express GraphQLLet’s begin with the basic project structure of a Node.js application. Begin a new project in a new folder.$ mkdir graphql-example $ cd graphql-exampleUse NPM to intiialize a project$ npm init -yInstall the required dependencies for Express, MongoDB (Mongoose), and some additional dependencies required for the function of Express.$ npm install express mongoose body-parser cors --saveApollo Server is a community-maintained open-source GraphQL server that works with all Node.js HTTP server frameworks, so next, you are going to download and save that.$ npm install apollo-server-express --saveThis should’ve created a package.json and a package-lock.json file within your folder. These files contain information regarding our environment, the dependencies, and the specific versions to run those dependencies.This means our environment is ready and you can now start developing the integrated server and API. We are going to write the Schema inside the index.js file. In the index.js file, start off by writing this code.const express = require('express'); const mongoose = require('mongoose'); const schema = require('./schema'); const bodyParser = require('body-parser'); const cors = require('cors'); const { ApolloServer } = require('apollo-server-express'); const url = "mongodb://localhost:27017/moviesdb"; const connect = mongoose.connect(url, { useNewUrlParser: true }); connect.then((db) => {       console.log('Connected correctly to server!'); }, (err) => {       console.log(err); }); const server = new ApolloServer({       typeDefs: schema.typeDefs,       resolvers: schema.resolvers }); const app = express(); app.use(bodyParser.json()); app.use('*', cors()); server.applyMiddleware({ app }); app.listen({ port: 4000 }, () =>   console.log(`Server ready at  http://localhost:4000${server.graphqlPath}`));In lines number 1 to 6, you’re implementing the necessary modules. Note that here you have imported the ./schema, but you haven’t created that yet. We will be doing this in the next step.In lines number 9 to 14, you are connecting the project to the MongoDB database and logging any error you face to the console.In lines number 16 to 19, you’re creating a new Apollo Server with typeDefs and Resolver. We’ll be defining those in the ./schema later in this tutorial.In lines 21 to 26, you’re firing up the Express Server at port 4000, when you will actually be able to interact with what you’re building.GraphQL has two main principles to work: types and resolvers. We defined them in Apollo Server. We’ll import them from the file you’ll create later.Next, let’s create the file models/movie.js that’ll contain the movie-Mongoose model.const mongoose = require('mongoose'); const Schema = mongoose.Schema; const movieSchema = new Schema({     name: {        type: String,        required: true     },     rating: {        type: Number,        required: true     },     producer: {        type: String,        required: true    } }, {     timestamps: true }); var Movies = mongoose.model('Movie', movieSchema); module.exports = {Movies, movieSchema};We’re going to build a simple movie app, where you can show, add, edit, and delete movies. That way you’ll get through the basics of GraphQL, which is the main goal of this tutorial.In lines 4 to 19, you’re basically determining the schema of the database that is going to hold the data of movies. Every movie is going to have a Name and a Producer of type String and a Rating of type Number.Designing the SchemaLet’s move on to the schema.js file where you’re going to build our GraphQL API.Create a new file in the root of the folder by the name of schema.js and add the following code.const { gql } = require('apollo-server-express');   const Movie = require('./models/movie').Movies;   const typeDefs = gql `    type Movie {      id: ID!      name: String!      producer: String!      rating: Float!  }  type Query {    getMovies: [Movie]    getMovie(id: ID!): Movie  }  type Mutation {      addMovie(name: String!, producer: String!, rating: Float!): Movie      updateMovie(id: ID!, name: String!, producer: String!, rating: Float): Movie      deleteMovie(id: ID!): Movie    } `In this, you’re building the schema. We defined the Movie type which will have an ID, the name of the movie and the producer, and a rating of type Float. The “!” after the types shows that these fields are necessary.Unlike the REST approach of getting different tasks done at different endpoint URLs, GraphQL can create operations in a single endpoint. That is what you have done in line 11 onwards. The type Query determines the GET operations, and type Mutation determines the modification operations like POST, DELETE, etc. In getMovies, you’re returning a list of all available movies in our database, and in getMovie, you’re getting the specific movie by the ID of that movie.Now you’re going to link these with the Mongoose Database queries that are going to perform the actions in the database. And this is done by Resolvers. Resolvers are a collection of functions that connect schema fields and types to various backends. It can read, write, and delete data from and to anywhere in the database, be it SQL, NoSQL, or Graph-based database. In simple terms, they act as a GraphQL query handler. Here’s how you’re going to implement Resolvers in our code:const resolvers = {   Query: {     getMovies: (parent, args) => {       return Movie.find({});     },     getMovie: (parent, args) => {       return Movie.findById(args.id);     }   },   Mutation: {     addMovie: (parent, args) => {       let movie = new Movie({         name: args.name,         producer: args.producer,         rating: args.rating,       });       return movie.save();     },     updateMovie: (parent, args) => {       if (!args.id) return;         return Movie.findOneAndUpdate(          {            _id: args.id          },          {            $set: {              name: args.name,              producer: args.producer,              rating: args.rating,            }          }, {new: true}, (err, Movie) => {            if (err) {              console.log('Something went wrong when updating the movie');            } else {              continue;            }          }       );     }   } } module.exports = {typeDefs,resolvers};This is the basic logic of MongoDB and CRUD applications, which doesn’t come under the scope of this article, since it is majorly focused on GraphQL. However, the logic is simple and straightforward for anyone to understand, so skim through it once.With this, you’re done with a basic Movie API that can perform all the CRUD operations on a database of movies. To test this out, you’re going to fire up our node server and open the browser in http://localhost:4000/graphql which will open the GraphQL Playground.$ node index.js Server ready at http://localhost:4000/graphqlOnce the Playground UI opens, you’re first going to create a Movie Record for the database since it would initially be empty.mutation { addMovie(name: “GraphQL Movie”, producer: “Facebook”, rating:  4.5) { id, name, rating, producer } }OUTPUT:{ “data” : { “addMovie”: { “id”: “5j2j1lnk1LNS231MLK3”, “name”: “GraphQL Movie”, “producer”: “Facebook”, “rating”: 4.5 } } }And now let’s list out all the movies in the database with only their “name” and “rating”.query { getMovies: { name, rating } }OUTPUT:{ “Data”: { “getMovies”: [ { “name”: “GraphQL Movie”, “rating”: 4.5 } ] } }So, you have successfully created a Movie API where you can perform all the CRUD operations on a single endpoint, and also ask for just the data that you want.  This results in a blazing fast API response and a developer-friendly return object that makes development fast and easy.Using GraphQL with ReactUsing GraphQL with react is super easy and can make full-stack development look like a piece of cake. We’re going to build a react app that uses the Movie API you just built to render the results on a frontend client app.Start off by installing the required dependencies.$ npm install create-react-app graphql @apollo/clientCreate a new React appnpx create-react-app movies-appLet’s start off by initializing an ApolloClient instance. In index.js let's first import the symbols you need from @apollo/client, Next, you'll initialize ApolloClient, passing its constructor a configuration object with URI and cache fields:import {   ApolloClient,   InMemoryCache,   ApolloProvider,   useQuery,   gql } from "@apollo/client"; const client = new ApolloClient({   uri: 'https://48p1r2roz4.sse.codesandbox.io',   cache: new InMemoryCache() });The URI specifies the GraphQL Server URL.That’s it! Our client app is ready to fetch data from the GraphQL server. In index.js, let’s wrap our React app with the ApolloProvider Component. Put up the ApolloProvider somewhere high in the app, above any component that might need to access GraphQL data.function App() {   return (           My first GraphQL app       ); } render(         ,   document.getElementById('root'), );With this being done, our client app is now ready to request data from the server and perform queries on the frontend. We can do this using the useQuery React Hook that shares the GraphQL data with the UI.In the index.js, let’s first define the query you want to execute.const MOVIES = gql`   query getMovies {      name,      producer   } `;Next, let's define a component called GetMovies that executes our getMovies query with the useQuery hook:function GetMovies() {   const { loading, error, data } = useQuery(MOVIES);   if (loading) return Loading...;   if (error) return Error :(;   return data.map(({ name, producer }) => (                   {name}: Produced by {producer}             )); }Whenever this component renders, the useQuery hook automatically executes our query and binds the results to the data property on successful completion of the query.Finally, you'll add GetMovies to our existing component tree:function App() {   return (           My first Apollo app             ); }When your app reloads, you should briefly see a loading indicator, followed by a list of Movies present in the MongoDB database.Congratulations. You just made a React app that uses GraphQL to render data from the server. Give yourself a pat on the back for this one.Dev-friendly Query Languages are the FutureSo, wrapping it all up in a few more lines. In this tutorial, you learned what GraphQL is - a new age Query Language that is data specific and client-oriented, how is it different (and better) than REST architecture - it is developer friendly, blazing-fast, and easy to learn or understand. We also made a mock API of Movies using GraphQL and MongoDB and performed the CRUD operations using just one single endpoint URL - another benefit over the RESTful architecture. And finally, you went on to create a React application that uses these benefits of GraphQL and combines them with the benefits of React to give a hyper-fast, easy, and full-stack app that renders Movies on request.We hope you learned something new from this article. Once you’ve started this journey of GraphQL, it is a fun ride ahead since it is a relatively new tech and not many people out there are having this skill under their hood. So, make use of this opportunity and outshine the rest.Keep Learning.
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Create GraphQL API with example

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How to use Timers in Node.js

You can use Node.js's utilities to schedule the execution of your code. The timer module, unlike most Node.js modules, is not imported. To comply with the JavaScript browser API, the methods are globally accessible.The Node.js Timers module contains several functions that allow you to execute a block of code or a function after a specified amount of time. You don't need to use require() to import the Timers module because it's global.In this post, I'll explain and demonstrate what timers are, how to use them, how the syntax looks, and how you can use them in your applications. For example, if you want to retrieve data from a REST API at a specific interval, you can easily do so with timers. So, even if you are unfamiliar with JavaScript or timers, this post will help you understand these concepts.The Event Loop - A Quick PrimerNode.js is a single-threaded, event-driven platform that can run non-blocking, asynchronous code. These Node.js features make it memory efficient. Even though JavaScript is single-threaded, the event loop enables Node.js to perform non-blocking I/O operations. It is accomplished by delegating tasks to the operating system whenever and wherever possible.Because most operating systems are multi-threaded, they can handle multiple operations that are running in the background. When one of these operations is finished, the kernel notifies Node.js, and the callback associated with that operation is added to the event queue, where it will eventually be executed.Features of Event Loop:An event loop is an infinite loop that waits for tasks, executes them, and then sleeps until more tasks are received.When the call stack is empty, i.e., there are no ongoing tasks, the event loop executes tasks from the event queue.We can use callbacks and promises in the event loop.The event loop executes the tasks in reverse order, beginning with the oldest.Example:console.log("One"); setTimeout(function(){ console.log("Two"); }, 1000); console.log("Three");Output:OneThreeTwoThe first console log statement is pushed to the call stack in the above example, and "One" is logged on the console before the task is popped from the stack. Following that, the setTimeout is added to the queue, the task is sent to the operating system, and the task's timer is set. After that, this task is removed from the stack. The third console log statement is then pushed to the call stack, "Three" is logged on the console, and the task is removed from the stack.Timers in JavaScriptA timer is used in JavaScript to execute a task or function at a specific time. The timer is essentially used to delay the execution of the program or to execute the JavaScript code at regular intervals. You can delay the execution of the code by using a timer. As a result, when an event occurs or a page loads, the code does not complete its execution at the same time.Advertisement banners on websites, which change every 2-3 seconds, are the best example of a timer. These advertising banners are rotated at regular intervals on websites such as Flipkart. To change them, you set a time interval.JavaScript provides two timer functions, setInterval() and setTimeout(), which help to delay code execution and allow one or more operations to be performed repeatedly.setTimeout():The setTimeout() function allows users to postpone the execution of code. The setTimeout() method accepts two parameters, one of which is a user-defined function, and the other is a time parameter to delay execution. The time parameter, which is optional to pass, stores the time in milliseconds (1 second = 1000 milliseconds).setInterval():The setInterval method is similar to the setTimeout() function in some ways. It repeats the specified function after a time interval. Alternatively, you can say that a function is executed repeatedly after a certain amount of time specified by the user in this function.Timers in Node.js - setTimeout()setTimeout() can be used to execute code after a specified number of milliseconds. This function is equivalent to window. setTimeout() from the browser JavaScript API, but no code string can be passed to be executed.setTimeout() takes a function to execute as the first argument and a millisecond delay defined as a number as the second. Additional arguments may be provided, and these will be passed to the function. As an example, consider the following:Using setTimeout()The timeout interval is not guaranteed to execute after that exact number of milliseconds. This is because any other code that blocks or holds onto the event loop will delay the execution of the timeout. The only guarantee is that the timeout will not be executed sooner than the timeout interval specified.setTimeout(function A() { return console.log('Hello World!'); }, 2000); console.log('Executed before A');clearTimeout():The clearTimeout() method deactivates a timer that was previously set with the setTimeout() method.The ID value returned by setTimeout() is passed to the clearTimeout() method as a parameter.Syntax:clearTimeout(id_of_settimeout)Example: function welcome () { console.log("Welcome to Knowledgehut!"); } var id1 = setTimeout(welcome,1000); var id2 = setInterval(welcome,1000); clearTimeout(id1);Timers in Node.js - setImmediate()To execute code at the end of the loop cycle, use the setImmediate() method. In layman's terms, this method divides tasks that take longer to complete, in order to run a callback function that is triggered by other operations such as events.Syntax:let immediateId = setImmediate(callbackFunction, [param1, param2, ...]); let immediateId = setImmediate(callbackFunction);The function to be executed will be the first argument to setImmediate(). When the function is executed, any additional arguments will be passed to it.Now consider the difference between setImmediate() and process. nextTick(), as well as when to use which.While processing, setImmediate() is executed in the Check handlers phase. process.nextTick() is called at the start of the event loop and at the end of each phase.process.nextTick() has higher priority than setImmediate():setImmediate(() => console.log('I run immediately')) process.nextTick(() => console.log('But I run before that'))Output:Using setImmediate()Multiple setImmediate functions are called in the following example. When you do this, the callback functions are queued for execution in the order in which they are created. After each event loop iteration, the entire callback queue is processed. If an immediate timer is queued from within an executing callback, it will not be triggered until the next iteration of the event loop.Example:setImmediate(function A() { setImmediate(function B() { console.log(1); setImmediate(function D() {   console.log(2); }); }); setImmediate(function C() { console.log(3); setImmediate(function E() {   console.log(4); }); }); }); console.log('Started');clearImmediate():The clearImmediate function is used to remove the function call that was scheduled by the setImmediate function. Both of these functions can be found in Node.js's Timers module.Example:console.log("Before the setImmediate call") let timerID = setImmediate(() => {console.log("Hello, World")}); console.log("After the setImmediate call") clearImmediate(timerID);Timers in Node.js - setInterval()This method, unlike setTimeout(), is used to execute code multiple times. For example, the company may send out weekly newsletters to its Edge as a Service customer. This is where the setInterval() method comes into play. It is an infinite loop that will continue to execute as long as it is not terminated (or halted).As the second argument, setInterval() accepts a function argument that will run an infinite number of times with a given millisecond delay. In the same way that setTimeout() accepts additional arguments beyond the delay, these will be passed on to the function call. The delay, like setTimeout(), cannot be guaranteed due to operations that may stay in the event loop and should thus be treated as an approximation.Syntax:let intervalId = setInterval(callbackFunction, [delay, argument1, argument2, ...]); //option 1 let intervalId = setInterval(callbackFunction[, delayDuration]); // option 2 let intervalId = setInterval(code, [delayDuration]); //option 3Using setInterval()Example:setInterval(function A() { return console.log('Hello World!'); }, 1000); // Executed right away console.log('Executed before A');setInterval(), like setTimeout() returns a Timeout object that can be used to reference and modify the interval that was set.In the above example, function A() will execute after every 1000 milliseconds.clearInterval():Example:var si = setInterval(function A() { return console.log("Hello World!"); }, 1000); setTimeout(function() { clearInterval(si); }, 4000);Using Timer.unref()The timer module is used to schedule functions that will be called later. Because it is a global API, there is no need to import (require("timers")) to use it.The Timeout Class contains an object (setTimeout()/setInterval()) that is created internally to schedule actions, and (clearTimeout()/clearInterval()) that can be passed to cancel those scheduled actions. When a timeout is set, the Node.js event loop will continue to run until clearTimeout() is called. The setTimeout() method returns timeout objects that can be used to control this default behaviour, and it exports both the timeout.ref() and timeout.unref() functions.timeout.ref():When the Timeout is active and (timeout.ref()) is called, it requests that the Node.js event loop not exit for an extended period of time. In any case, calling this Method multiple times has no effect.Syntax:timeout.ref()timeout.unref():When the Timeout is enabled, the Node.js event loop is not required to remain active. If any other activity keeps the event loop running, the Timeout object's callback is invoked after the process exits. In any case, calling this Method multiple times has no effect.Syntax:timeout.unref()Example:var Timeout = setTimeout(function alfa() { console.log("0.> Setting Timeout", 12); }); console.log("1 =>", Timeout.ref()); Timeout.unref() Timeout.ref() console.log("2 =>", Timeout.unref()); clearTimeout(Timeout); console.log("3 => Printing after clearing Timeout"); Output:Scheduling Made SimplerIn this tutorial, you learned how to schedule tasks with the Node.js timer module. You've seen how to set timeouts, interval timers for recurring tasks, and how to use set immediate to bypass long operations. You've also seen how to stop these operations using the clear() method for each method.As with learning anything new, practising what you learn will make a big difference to how easily you can perform these tasks. Share your thoughts and questions in the comments as you try out what you’ve learnt.
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How to use Timers in Node.js

You can use Node.js's utilities to schedule the ex... Read More