Run Node.js scripts from the command line

The usual way to run a Node.js program is to run the globally available node command (once you install Node.js) and pass the name of the file you want to execute.

If your main Node.js application file is app.js, you can call it by typing:

node app.js

Above, you are explicitly telling the shell to run your script with node. You can also embed this information into your JavaScript file with a "shebang" line. The "shebang" is the first line in the file, and tells the OS which interpreter to use for running the script. Below is the first line of JavaScript:

#!/usr/bin/node

Above, we are explicitly giving the absolute path of interpreter. Not all operating systems have node in the bin folder, but all should have env. You can tell the OS to run env with node as parameter:

#!/usr/bin/env node

// your javascript code

To use a shebang, your file should have executable permission. You can give app.js the executable permission by running:

chmod u+x app.js

While running the command, make sure you are in the same directory which contains the app.js file.

Pass string as argument to node instead of file path

To execute a string as argument you can use -e, --eval "script". Evaluate the following argument as JavaScript. The modules which are predefined in the REPL can also be used in script.

On Windows, using cmd.exe a single quote will not work correctly because it only recognizes double " for quoting. In Powershell or Git bash, both ' and " are usable.

node -e "console.log(123)"

Restart the application automatically

As of nodejs V16, there is a built-in option to automatically restart the application when a file changes. This is useful for development purposes. To use this feature, you need to pass the `--watch' flag to nodejs.

node --watch app.js

So when you change the file, the application will restart automatically. Read the --watch flag documentation.