process is a global object that provides information about, and control over, the current Node.js process. It's your interface to the environment, command-line arguments, I/O streams, lifecycle, and signals.
process..;
process..;
port = process.. || ;
process.env is the standard way to read configuration and secrets (set outside the code) — central to twelve-factor config.
// node script.js --name=Ann
process.argv; // ["node", "/path/script.js", "--name=Ann"]
const args = process.argv.slice(2); // skip the first two
process.stdout.write("output\n"); // console.log writes here
process.stderr.write("error\n"); // console.error writes here
process.stdin.on("data", (chunk) => { /* read input */ });
process.exit(0); // exit with success code (1 = error)
process.exitCode = 1; // preferred: set code, let the process finish naturally
process.pid; // the process id
process.cwd(); // current working directory
process.uptime(); // seconds the process has run
process.on("SIGTERM", () => { /* clean up, then exit — e.g. on container stop */ });
process.on("SIGINT", () => { /* Ctrl+C */ });
process.on("uncaughtException", (err) => { log(err); process.exit(1); });
process.on("unhandledRejection", (reason) => { log(reason); });
Listening for SIGTERM/SIGINT is how you implement graceful shutdown (finish in-flight requests, close DB connections before exiting), and the uncaught-error handlers are last-resort safety nets.
process.memoryUsage(); // heap stats (leak detection)
process.nextTick(cb); // schedule a callback before the next event-loop phase
process.platform; // "linux" | "darwin" | "win32"
process is your program's connection to its runtime environment.
You use it constantly: reading config/secrets via process.env, handling CLI args, and — importantly for production — catching signals for graceful shutdown and last-resort error handlers.
Understanding it is essential for building configurable, robust, production-ready Node applications.