We’ve made major improvements to JavaScript debugging in Firefox DevTools over the past two years. Developer feedback has informed and validated our work on performance, source maps, stepping reliability, pretty printing, and more types of breakpoints. Thank you. If you haven’t tried Firefox for debugging modern JavaScript in a while, now is the time.

Many of the aforementioned efforts focused on the Debugger frontend (written in React and Redux). We were able to make steady progress. The integration with SpiderMonkey, Firefox’s JavaScript engine, was where work went more slowly. To tackle larger features like proper asynchronous call stacks (available now in DevEdition), we needed to do a major cleanup. Here’s how we did that.

#debugging #firefox #javascript #programming