What are the best practices for using HTML5 web workers to improve web page performance?

1 Create web workers only when needed

Creating a web worker involves some overhead, such as loading the script file, initializing the worker context, and setting up the message handlers. Therefore, you should avoid creating too many web workers or creating them unnecessarily. Instead, you should create web workers only when you need to run a task that is computationally intensive, long-running, or independent of the main thread. You can also reuse web workers for multiple tasks by sending different messages or parameters.

2 Use transferable objects to pass data

When you send data from the main thread to a web worker or vice versa, the data is copied by default. This can be inefficient and memory-intensive, especially for large or complex data types, such as arrays, blobs, or files. To optimize this process, you can use transferable objects, which are data types that can be transferred from one context to another without copying. When you transfer an object, you lose access to it in the original context, but you gain performance and memory benefits. To use transferable objects, you need to pass them as the second argument of the postMessage method, in an array.

3 Terminate web workers when not in use

Web workers are not automatically terminated when they finish their tasks or when the page is closed. They keep running in the background and consuming resources, unless you explicitly terminate them. To do this, you can use the terminate method on the main thread or the close method on the worker thread. You should also add event listeners for the unload or beforeunload events on the main thread, to terminate any active web workers when the page is unloaded. This will prevent memory leaks and improve performance.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?