20210903 - Set Environment Variables & Deal with missing dependencies

Well, I’ve just known how to set environment variables.

1. Create a .env (just the name ‘.env’ is fine) file in the root of your project
2. In the file, add this line: # env REACT_APP_API_KEY=[your_app_api_key]
3. Add const api_key = process.env.REACT_APP_API_KEY to where you need the key
4. Hide your key by adding ‘.env’ file into gitignore, so that file wont be pushed to github, once you do commit

When every step was done, I did set the key and run the application successfully.

But here’s another error I got. I can’t figure out what it means:

react_devtools_backend.js:2850 src\components\Weather.js Line 22:6: React Hook useEffect has missing dependencies: ‘api_key’ and ‘profile.capital’. Either include them or remove the dependency array react-hooks/exhaustive-deps

Actually I remember I got this error last time and solved it finally. But this time it’s weird, like, why it had to mention api_key here? And what’s this dependency array exactly???

Solutions from stackoverflow, but I haven’t tested yet.

How to fix missing dependency warning when using useEffect React Hook