In the beginning, there were configuration files. Each environment had one committed to our repositories. Then, we discovered the light of the 12-factor applications and having environment-specific values set as environment variables. Then, NODE_ENV came along, and it broke our idyllic world.
Libraries with millions of weekly downloads check for NODE_ENV=production to enable optimizations, changing the behavior of applications. Given this worked so well, developers started loading configuration files (or secrets) based on the value of NODE_ENV to identify _their_ "production" environment.
However, what value should be used for the staging environment? What about QA? If we don't run the same code everywhere, we will be hit by bugs that we cannot reproduce across environments. So, we set NODE_ENV=production everywhere. How should we distinguish across environments, then? We took a look in this video
