At what point are the environments set?

Question

Node.js

When are environment variables set? eg process.env
At application build time?

Answer 1

The very name of environment variables implies that they are set by the environment when the program starts.
[telepathy] however, judging by the React tag, you have code for the browser that is being assembled by something (webpack, rollup, etc.) and these assemblers can replace process.env at the build stage right in the code.