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Napa.js: a multi-threaded JavaScript runtime

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Napa.js is a multi-threaded JavaScript runtime built on V8, which was originally designed to develop highly iterative services with non-compromised performance in Bing. As it evolves, we find it useful to complement Node.js in CPU-bound tasks, with the capability of executing JavaScript in multiple V8 isolates and communicating between them. Napa.js is exposed as a Node.js module, while it can also be embedded in a host process without Node.js dependency.


Install the latest stable version:

npm install napajs
Other options can be found in Build Napa.js.

Quick Start

const napa = require('napajs');
const zone1 ='zone1', { workers: 4 });

// Broadcast code to all 4 workers in 'zone1'. zone1.broadcast('console.log("hello world");');

// Execute an anonymous function in any worker thread in 'zone1'. zone1.execute( (text) => text, ['hello napa']) .then((result) => { console.log(result.value); });

More examples: * Estimate PI in parallel * Max sub-matrix of 1s with layered parallelism * Parallel Quick Sort * Recursive Fibonacci with multiple JavaScript threads * Synchronized loading


  • Multi-threaded JavaScript runtime.
  • Node.js compatible module architecture with NPM support.
  • API for object transportation, object sharing and synchronization across JavaScript threads.
  • API for pluggable logging, metric and memory allocator.
  • Distributed as a Node.js module, as well as supporting embed scenarios.



You can contribute to Napa.js in following ways:

  • Report issues and help us verify fixes as they are checked in.
  • Review the source code changes.
  • Contribute to core module compatibility with Node.
  • Contribute bug fixes.

This project has adopted the Microsoft Open Source Code of Conduct.
For more information see the Code of Conduct FAQ or contact [email protected] with any additional questions or comments.


Copyright (c) Microsoft Corporation. All rights reserved.

Licensed under the MIT License.

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