Multithreaded Javascript

Chapter 4. Shared Memory

So far you’ve been exposed to the web workers API for browsers, covered in Chapter 2, and the worker threads module for Node.js, covered in “The worker_threads Module”. These are two powerful tools for working with concurrency in JavaScript, allowing developers to run code in parallel in a way that wasn’t previously available to JavaScript.

However, the interaction you’ve had with them so far has been fairly shallow. While it’s true they allow you to run code in parallel, you’ve only done so using message-passing APIs, ultimately depending on the familiar event loop to handle the receipt of a message. This is a much less performant system than the threading code you worked with in “Threads in C: Get Rich with Happycoin” where these disparate threads are able to access the same shared memory.

This chapter covers two powerful tools available to your JavaScript applications: the Atomics object and the SharedArrayBuffer class. These allow you to share memory between two threads without depending on message passing. But before diving into a complete technical explanation for these objects, a quick introductory example is in order.

In the wrong hands, the tools covered here can be dangerous, introducing logic-defying bugs to your application that slither in the shadows during development only to rear their heads in production. But when honed and used properly, these tools allow your application to soar to new heights, squeezing never-before-seen levels of performance ...