Node.js Worker.isMainThread Property

The Worker.isMainThread property an inbuilt application programming interface of class Worker within worker_threads module which is used to check if the current thread is running  inside the worker thread or not.

Syntax:

const Worker.isMainThread

Parameters: This property does not accept any parameter.

Return Value: This property returns the Boolean value true if the current thread is running not inside the worker thread otherwise false.

Example 1: Filename: index.js

javascript

// Node.js program to demonstrate
// the Worker.isMainThread  API

// Importing worker_thread module
const { Worker, isMainThread } = require('worker_threads');

// Checking if the current thread is inside the
// Main thread or not by using IsMainThread API
if (isMainThread) {
  console.log('OutSide Worker!2');
  console.log('1');
  console.log('2');
  console.log('3');
  console.log(isMainThread);
}

Run the index.js file using the following command:

node index.js

Output:

OutSide Worker!2
1
2
3
true

Example 2: Filename: index.js

javascript

// Node.js program to demonstrate the
// Worker.isMainThread  API

// Importing worker_thread module
const { Worker, isMainThread }
    = require('worker_threads');

// Checking if the current thread is
// inside the main thread or not
// by using IsMainThread API
if (isMainThread) {

   // This re-loads the current file
   // inside a Worker instance.
   new Worker(__filename);
} else {
  console.log('Inside Worker!2');
  console.log('1');
  console.log('2');
  console.log('3');
  console.log(isMainThread);
}

Run the index.js file using the following command:

node index.js

Output:

Inside Worker!2
1
2
3
false

Reference: https://nodejs.org/dist/latest-v12.x/docs/api/worker_threads.html#worker_threads_worker_ismainthread