WARNING – YOU WILL EXPOSE YOUR COMPUTER TO THE WORLD…

Simplest option ever: local tunnel

Even if you have a dynamic IP, or you’re under a NAT, you can deploy your app and serve the requests right from your computer using a local tunnel.  This option is suited for some quick testing, demo a product or sharing of an app with a very small group of people.

A very nice tool for this, available on all platforms, is ngrok.
Using it, you can just type ngrok PORT and the PORT you want is exposed to the internet. You will get a ngrok.io domain, but with a paid subscription you can get a custom URL as well as more security options (remember that you are opening your machine to the public Internet).

Another service you can use is https://github.com/localtunnel/localtun