Firefox 78: Protections Dashboard, New Developer Features, and the End of the Line For Older MacOS Versions (theregister.com) 51
Developers get a bunch of new features. The Accessibility inspector is out of beta -- this is a tab in the developer tools that will check a page for accessibility issues when enabled. Source maps are a JavaScript feature that map minified code back to the original code to make debugging easier. Firefox has a Map option that lets you use source maps in the debugger, and this now works with logpoints, a type of breakpoint that writes a message to the console rather than pausing execution, so that you see the original variable names. Mozilla has also worked on debugging JavaScript promises, so you can see more detail when exceptions are thrown.
A big feature for debugging web applications when running on mobile is the ability to connect an Android phone with USB, and navigate and refresh mobile web pages from the desktop. Patience is required though, since this will only work with a forthcoming new version of Firefox for Android. Mozilla has been working on a new Regular Expression (RegExp) evaluator and this is included in SpiderMonkey (Mozilla's JavaScript engine) in Firefox 78. This brings the evaluator up to date with the requirements of ECMAScript 2018.