Node Fundamentals: Process

This is a series of posts that will illustrate the what, why and how of Node. I'll be sharing my learnings from a course on Advanced NodeJS by Samer Buna offered on PluralSight. Any code samples tagged or attached will be available at the following repo.

jscomplete / advanced-nodejs

For help, ask in #questions at slack.jscomplete.com

process Object

process object provides a bridge between a Node application and its running environment.

process object is an instance of event-emitter. So we can emit and listen to events on the object

Useful properties and events

• pid: Outputs the process id on OS level.

• version: Read dependencies and versions
  

$ node -p "process.version"
{
  node: '13.12.0',
  v8: '7.9.317.25-node.30',
  uv: '1.35.0',
  zlib: '1.2.11',
  brotli: '1.0.7',
  ares: '1.16.0',
  modules: '79',
  nghttp2: '1.40.0',
  napi: '6',
  llhttp: '2.0.4',
  openssl: '1.1.1e',
  cldr: '36.1',
  icu: '66.1',
  tz: '2019c',
  unicode: '13.0'
}

• env - Lists all environment variables. Better to always read values from a layer above it using config.

• release.lts - node -p "process.release.lts" will be undefined if not on LTS version of node.

• exit event - Will be invoked when the application has nothing else to do or a manual process.exit call is made.
  

process.on("exit", (code) => {
  // do one final synchronous operation
  // before node process terminates.
  // can't stop termination at this point
});

• uncaughtException event - Will invoke when an error is not caught in the application. If not registered, node will print the stack trace and terminate. When it is registered, node will not terminate and will stay in an unstable state. It's better to forcefully terminate the process when this event is invoked.

process.on("uncaughtException", (err) => {
  // something wnet unhandled
  // Do any cleanup and EXIT forcefully.
});