How to set automatically call "npm start" in nodejs?

node-dev will automatically restart your application whenever you save a code change. Install it with npm install -g node-dev then run your application with node-dev server.js (or whatever the entrypoint file for your project is called if not server.js).

For development, it's easiest to just live with the port in the URL. To get rid of it, you need to run your application on port 80 which requires running as root which is insecure. There are ways to do it (via ngrok iptables, nginx, etc, but most developers opt to just deal with the port in the URL during local development

Try nodemon module, Nodemon is a utility that will monitor for any changes in your source and automatically restart your server.Perfect for development on local machine, you no longer need to deal with npm start every time when you change the code.It will automatically restart the server and changes will be reflect instantly.

install it globally

npm install -g nodemon

then try to run your app using nodemon app.js instead of npm start or node app.js

If you want to use port 80, you should run your application with root/administrator privileges, and make sure no other service is running on that port another solution is which I strongly recommend is to use nginx server reverse proxy settings .Install nginx server on your machine, Following are the settings that you can apply using nginx reverse proxy to remove any port number you want from the url.

server {
        listen   80;
        server_name yourdomain.com;

        location / {
                proxy_set_header X-Real-IP $remote_addr;
                proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
                proxy_set_header Host $host;
                proxy_set_header X-NginX-Proxy true;
                proxy_pass http://localhost:3000/;
                proxy_redirect http://localhost:3000/ https://$server_name/;
        }
}

Hope this helps you.