The inspector module provides an API that makes it easy to interact with the V8 inspector.

Opening an Inspector

One can easily open an inspector like:

const inspector = require("inspector");

inspector.open(); // <- inspector.open([port[, host[, wait]]])
/*
Debugger listening on ws://127.0.0.1:9229/ab01a630-90ad-4c87-91c9-a665632c1d8b
For help see https://nodejs.org/en/docs/inspector
*/

inspector.url();
// 'ws://127.0.0.1:9229/ab01a630-90ad-4c87-91c9-a665632c1d8b'

inspector.console.log("This should be visible on the debugger console");

Waiting for Debugger

Most of the time we would want to wait until the debugger is connected to our process. That’s where inspector.waitForDebugger() will be useful:

// foo.js
(() => {
  const inspector = require("inspector");
  inspector.open();
  inspector.waitForDebugger();
})();

> node foo.js
# This would make the process wait till the debugger is connected.
# Debugger listening on ws://127.0.0.1:9229/b4b0e48d-2e4c-4cde-8177-6924c662aef4
# For help, see: https://nodejs.org/en/docs/inspector
# Debugger attached.
# Waiting for the debugger to disconnect...

Session API

Dispatching and receiving message responses and notifications is possible with the session API:

const inspector = require("inspector");

inspector.open();
inspector.waitForDebugger();

const session = new inspector.Session();

session.on("inspectorNotification", (message) => console.log(message.method));
// Debugger.paused
// Debugger.resumed

session.post("Runtime.evaluate", { expression: "5 + 4" }, (error, { result }) =>
  console.log(result)
);
// 9

session.on(<inspector-protocol-method>) where the methods are from devtools-protocol.

P.S: This is an experimental API with Stability of 1, meaning it is not subject to Semantic Versioning rules. Non-backward compatible changes or removal may occur in any future release. Use of the feature is not recommended in production environments.