Chapter 3
Managing Asynchronous Events

If you’re anything like me, at some point you’ve played a video game. And if you’ve played a video game, you’ve been frustrated at how long it takes things to load. A long time ago, I waited patiently for a game to load on our 56k connection, not realizing that something had failed and the loading bar’s status would be stuck at 99% for all eternity. Many years later, I’m getting my revenge by griping about it in a programming book. Right, back on topic.

At this point in your RxJS journey, you may feel like that old Wendy’s commercial: “Sure, Pig Latin was fun, but where’s the beef?” This is the beef chapter you’ve been waiting for. You’ll dive into asynchronous programming on top of RxJS and never look at an AJAX call the same way again. So much of frontend coding is tied up in handling multiple AJAX calls around the internet.

Until this chapter, RxJS has been merely convienent. In this chapter, you’ll build a progress bar. OK, progress bars aren’t terribly exciting, but there’s a lot wrapped up in there. Your attitude toward RxJS will shift from “convenient” to “indispensible” after you see how well RxJS handles multiple asynchronous requests flying around without breaking a sweat. Along the way, you’ll learn about making AJAX requests with Rx, error handling, a swath of new operators, and advanced uses of subscribe.