Is it possible to use .env in a React Web project?

I'm developing a PWA SPA with React Web, and practically everything is in .js.

I need to create environment variables in the Azure Portal, and as shown below I have already created some:

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However, I can't use it in my project that is already hosted on the Azure Portal:

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Any tip is welcome. I am sorry for my english.

The problem was resolved, I needed to make a request to the Azure Portal specialist team to restart the service after setting the environment variables.