This is the question mostly asked by the beginners, as I had this question when I was starting out
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*How to set port for **express** without needing to hardcode or even choose port yourself?* This is the question I had when I was starting out in node and express (I am still a beginner, have lots of things to learn). Things I wanted know other than that included,

* What is **difference between** using `app.set('port', portNum)` and directly using port number in `app.listen(portNum)`?