Debugging TypeScript Applications

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Debugging TypeScript Applications

Now in beta

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Dave's notes…

It's funny: when I learn a language, I'll spend hours exploring the edge cases and arcane syntax corners. But then, when it comes to debugging code in that language, I fall back on setting breakpoints and printing values; primitive and inefficient.

When it comes to debugging JavaScript or TypeScript in the browser, it turns out that I was only using 1% of the amazing developer tools environment.

A couple of pages into chapter one I discovered local overrides, which let you make persistent source changes in the browser.

In the next chapter, I learned about console.count() and also discovered how to add CSS styling to console messages. There's also a really useful object and function wrapper which will log all accesses.

It's Also About The Process

The book then takes a 90º turn with a fascinating chapter on bug triage: which do you fix first, and why? It even dives into using PERT and RICE to estimate a bug's impact. This is followed by a chapter on forensics and root-cause analysis: the five whys, failure trees, and the scientific method. The process section ends with a chapter somewhat grandly named Designing Software That Doesn’t Break. I think this chapter alone is worth the price of the book.

Back To The Debugger

How do you identify a bug that messes up some value that causes some entirely different piece of code to fail? That's what we look at next, as we explore all the source-code features available in the debugger. Here I learned about the global variable feature which lets you access a local, private value as if it were global: you can even change it while the code is running. I also learned there are nine different breakpoint types; I wish I'd known about log points years ago; they'd have saved me so much time.

The chapter on Debugging Asynchronous Operations is also a goldmine, particularly for applications with lots of network traffic behind every page.

Debugging is the Tardis of Software Practices…

…because there's a lot more on the inside that is apparent from the outside.

I thought I knew a lot about debugging. This book proved me wrong, and I'm a better developer for it.