The process object in Node.js is a global object that can be accessed inside any module without requiring it. There are very few global objects or properties provided in Node.js and process is one of them. It is an essential component in the Node.js ecosystem as it provides various information sets about the runtime of a program.

To explore we will use one of its properties which is called process.versions. This property tells us the information about Node.js version we have installed. It has to be used with -p flag.

$ node  -p "process.versions"

# output
{ http_parser: '2.8.0',
  node: '8.11.2',
  v8: '6.2.414.54',
  uv: '1.19.1',
  zlib: '1.2.11',
  ares: '1.10.1-DEV',
  modules: '57',
  nghttp2: '1.29.0',
  napi: '3',
  openssl: '1.0.2o',
  icu: '60.1',
  unicode: '10.0',
  cldr: '32.0',
  tz: '2017c' }

Another property you can check is process.release that is the same as the command $ node --version which we used when we installed Node.js. But the output this time is going to be more detailed.

node -p "process.release"

# output
{ name: 'node',
  lts: 'Carbon',
  sourceUrl: '',
  headersUrl: '' }

These are some of the different commands that we can use in a command line to access information that otherwise no module can provide.

This process object is an instance of the EventEmitter class. It does it contain its own pre-defined events such as exit which can be used to know when a program in Node.js has completed its execution.

Run the below program and you can observe that the result comes up with status code 0. In Node.js this status code means that a program has run successfully.

process.on('exit', code => {
	setTimeout(() => {
		console.log('Will not get displayed');
	}, 0);

	console.log('Exited with status code:', code);
console.log('Execution Completed');

Output of the above program:

Execution Completed
Exited with status code: 0

Process also provides various properties to interact with. Some of them can be used in a Node application to provide a gateway to communicate between the Node application and any command line interface. This is very useful if you are building a command line application or utility using Node.js

  • process.stdin: a readable stream
  • process.stdout: a writable stream
  • process.stderr: a wriatable stream to recognize errors

Using argv you can always access arguments that are passed in a command line. argv is an array which has Node itself as the first element and the absolute path of the file as the second element. From the third element onwards it can have as many arguments as you want.

Try the below program to get more insight into how you can use these various properties and functions.

process.stdout.write('Hello World!' + '\n');

process.argv.forEach(function(val, index, array) {
	console.log(index + ': ' + val);

If you run the above code with the following command you will get the output and the first two elements are of argv are printed.

$ node test.js

# output
Hello World!
0: /usr/local/bin/node
1: /Users/amanhimself/Desktop/articles/nodejs-text-tuts/test.js