1) JSdoc
Documenting code is very essential as it provide better readabilty to other programmers.
< https://www.valentinog.com/blog/jsdoc/ >
2) ESlint
Code linting is essential for developement, for finding problem early and fixing them.
3) Jest
Jest is powerful javascript unit testing framework which helps you with automated testing.
< https://www.youtube.com/watch?v=FgnxcUQ5vho >
4) Babel
< https://babeljs.io/docs/en/ >
5) Testing FireBase cloud functions
< https://firebase.google.com/docs/functions/unit-testing >
6) Unit testing react native apps
< https://jestjs.io/docs/tutorial-react-native >
< https://blog.logrocket.com/unit-testing-react-native/ >
Some more :
< https://everyday.codes/javascript/7-really-good-reasons-not-to-use-typescript/ >