December 18, 2018
This is not going to be a deep dive into Node’s environmental variables, but rather a quick look at how you may use environmental variables. I wanted to test load balancing an application. This meant I needed a way to dynamically set the port my server would listen on. This, it turns out, is a great example of how to use environmental variables provisioned from the command line. These can then be referenced from within the app to set variables - in my case
In my server file,
index.js, I defined my port as:
const port = process.argv || 8081. This says that if I fail to pass an explicit port, I will use the default 8081. However, I can also pass in a variable after node (process.argv), the file node is running (process.argv) and it will be mapped to my port variable.
// sh # In one terminal window $ node server/index.js 8082 listening on port 8082 # In a different terminal window $ node server/index.js 8083 listening on port 8083
This is a simple use case. It was also one of the first use cases I came across that helped me see how the process arguments worked in Node.js.
Written by Stephen Weiss who lives in Chicago with his wife, Kate, and dog, Finn. Follow him on Twitter!