How to pass argument in command line with npm and read it in react javascript code

Question

I run the react application using npm start which in package.json is defined as "start": "react-scripts start -o" . in the js code I have

const backendUrl = 'hardCodedUrl';

I want this property to be passed as CLI argument. like:

npm start url=newUrl

and read this in the javascript code at runtime to be able to set backendUrl. How Can I do this?

Answer 1

So I visited the link Andy sent and here is how I did it: Because I'm on Windows and using Terminal with PowerShell, run:

$env:REACT_APP_TT_BACKEND_URL = "Thank you Andy"
npm start

In the code

console.log('REACT_APP_TT_BACKEND_URL', process.env.REACT_APP_TT_BACKEND_URL);