What's New in Node.js 19

The Node.js team recently announced version 19 and  Node.js 18 will become Long-Term Support (LTS).

According to the Node.js release process, Node.js 19 will not be promoted to LTS as only even-numbered versions are promoted to LTS releases – like Node.js 8, Node.js 10, Node.js 12, and so on–will become LTS.

This version comes with  6 major features:

–watch

If you have used nodemon in the development process before, this feature will be very useful for you.
Node.js 19 comes with a "--watch" feature experimentally. To put it simply, your server restarts when there is a change in any file with "--watch" command line option which saves you time instead of restarting it over and over.

HTTP(S)/1.1 KeepAlive by default

const http = require("node:http");
console.log(http.globalAgent);
const https = require("node:https");
console.log(https.globalAgent);

Any outgoing HTTP(s) connection will automatically use HTTP 1.1 Keep-Alive. so HTTP  won't create a new TCP connection for every request. it will use an existing connection.

if you run the code you will see keepAlive is true. Before Node.js 19 it was false

Agent {
  _events: [Object: null prototype] {
    free: [Function (anonymous)],
    newListener: [Function: maybeEnableKeylog]
  },
  _eventsCount: 2,
  _maxListeners: undefined,
  defaultPort: 80,
  protocol: 'http:',
  options: [Object: null prototype] {
    keepAlive: true,
    scheduling: 'lifo',
    timeout: 5000,
    noDelay: true,
    path: null
  },
  requests: [Object: null prototype] {},
  sockets: [Object: null prototype] {},
  freeSockets: [Object: null prototype] {},
  keepAliveMsecs: 1000,
  keepAlive: true,
  maxSockets: Infinity,
  maxFreeSockets: 256,
  scheduling: 'lifo',
  maxTotalSockets: Infinity,
  totalSocketCount: 0,
  [Symbol(kCapture)]: false
}
Agent {
  _events: [Object: null prototype] {
    free: [Function (anonymous)],
    newListener: [Function: maybeEnableKeylog]
  },
  _eventsCount: 2,
  _maxListeners: undefined,
  defaultPort: 443,
  protocol: 'https:',
  options: [Object: null prototype] {
    keepAlive: true,
    scheduling: 'lifo',
    timeout: 5000,
    noDelay: true,
    path: null
  },
  requests: [Object: null prototype] {},
  sockets: [Object: null prototype] {},
  freeSockets: [Object: null prototype] {},
  keepAliveMsecs: 1000,
  keepAlive: true,
  maxSockets: Infinity,
  maxFreeSockets: 256,
  scheduling: 'lifo',
  maxTotalSockets: Infinity,
  totalSocketCount: 0,
  maxCachedSessions: 100,
  _sessionCache: { map: {}, list: [] },
  [Symbol(kCapture)]: false
}

Stable WebCrypto API

The Web Crypto API is now stable in Node.js 19 with some  exception of these algorithms: Ed25519, Ed448, X25519, and X448). you can check the algorithm matrix

Use globalThis.crypto or require('node:crypto').webcrypto to access this module.

Custom ESM resolution adjustments

Node.js has removed the --experimental-specifier-resolution flag. Its functionality can now be achieved via custom loaders.

Dropped DTrace/SystemTap/ETW support

DTrace can be used to get an overview of the system like memory, CPU , filesystem, and network resources. The reason behind this decision is the lack of resources to keep it up-to-date.

V8 JavaScript engine is updated to V8 10.7

Node.js 19  will use version 10.7 of the V8 JavaScript engine which is part of Chromium 107. This version includes a new feature to the JavaScript API: Intl.NumberFormat.