Everything is a task

When we visit a web page, a whole environment is created for us within the browser. This environment has several subsystems that enable the webpage we're looking at to look and behave as it should according to World Wide Web Consortium (W3C) specs. Tasks are the fundamental abstraction inside a web browser. Anything that happens is either a task itself, or a smaller part of a larger task.

Note

If you're reading any of the W3C specifications, the term "user agent" is used instead of "web browser". In 99.9% of cases, the major browser vendors are what we're reading about.

In this section, we'll look at the major components of these environments, and how task queues and event loops facilitate the communication between these components, to realize the overall appearance and behavior of the web page.

Meet the players

Let's introduce some terminology that will help us throughout the various sections in this chapter:

• Execution environment...