How to change value of process.env.PORT in node.js?

Question

For just one run (from the unix shell prompt):

$ PORT=1234 node app.js

More permanently:

$ export PORT=1234
$ node app.js

In Windows:

set PORT=1234

In Windows PowerShell:

$env:PORT = 1234

You can use cross platform solution https://www.npmjs.com/package/cross-env

$ cross-env PORT=1234

use the below command to set the port number in node process while running node JS programme:

set PORT =3000 && node file_name.js

The set port can be accessed in the code as

process.env.PORT 

EDIT: Per @sshow's comment, if you're trying to run your node app on port 80, the below is not the best way to do it. Here's a better answer: How do I run Node.js on port 80?

Original Answer:

If you want to do this to run on port 80 (or want to set the env variable more permanently),

1. Open up your bash profile vim ~/.bash_profile
2. Add the environment variable to the file export PORT=80
3. Open up the sudoers config file sudo visudo
4. Add the following line to the file exactly as so Defaults env_keep +="PORT"

Now when you run sudo node app.js it should work as desired.