React Native Error - yarn' is not recognized as an internal or external command

Question

I am not able to run the sample react Native AwesomeProject project.

Can anyone help? Below is the details.

C:\Users\dip\AwesomeProject>react-native run-android 'yarn' is not recognized as an internal or external command, operable program or batch file.
Scanning 557 folders for symlinks in C:\Users\dip\AwesomeProject\node_mo ules (31ms)
JS server already running.
Building and installing the app on the device (cd android && gradlew.bat instal Debug)...
Error occurred during initialization of VM
java/lang/NoClassDefFoundError: java/lang/Object
Could not install the app on the device, read the error above for details. Make sure you have an Android emulator running or a device connected and have set up your Android development environment:
https://facebook.github.io/react-native/docs/android-setup.html

Solution 1

Yarn is a tool created by facebook as an efficient alternative for npm. In your case.. it is just informing that Yarn is not installed in your system. It is not the culprit.

The problem lies in Error occurred during initialization of VM java/lang/NoClassDefFoundError: java/lang/Object Could not install the app on the device line. It looks like an error with the Java installation.

Solution: Go to C:\Windows\System32 directory and delete java.exe (or rename it to something like java.exe.old)

refer this answer for more details https://stackoverflow.com/a/30577609/5597641.

btw you can install Yarn by typing npm install -g yarn in your command prompt.

Solution 2

I faced the same issue and it got resolved by below command

npm install -g yarn

Solution 3

you have to install yarn globally in your windows OS type this in CMD

npm install -g yarn

you can check yarn version by typing yarn --version on CMD

Solution 4

You should probably insert your Yarn folder in your Environment Variables.

If you already performed the command

npm install -g yarn

and still can't use yarn via terminal, check the following folder: C:\Users\[your user]\AppData\Roaming\npm

If there`s a yarn file there, just put that directory in your Path variable.

Solution 5

Go here https://yarnpkg.com/en/docs/install

Install

Restart any terminals you had open.

yarn -v

...for confirmation

You should be good to go

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Comments

[Brian Lacy]

Note: If you don't have administrator privileges on your system, npm install -g yarn will not add yarn to your executable path, which will produce this error.

[Bama]

this resolved my issue after installing yarn via choco (failed to run on yarn install)

[Oleg Polezky]

for Windows after changing system environments you need to close and reopen the terminal

[Imran_Developer]

After running this command it was not working for me, then I go to C:\Users\<username>\AppData\Roaming\npm and deleted yarn.ps1 then it works!