Firefox 78 - New Extended Support Release
Written by Ian Elliot   
Tuesday, 07 July 2020

Firefox 78 includes a new RegExp evaluator, bringing it up to date with the requirements of ECMAScript 2018, and enhanced support for WebAssembly.

It only seems like yesterday that we reported Developer Tool Improvements In Firefox 77, but as Firefox 78 is an Extended Support Release (ESR) it merits renewed coverage. Mozilla provides a new Extended Support Release for enterprise users once a year and it includes all of the enhancements since the last ESR, in this case Firefox 68, together with the latest features. 

As far as users are concerned, the Protections Dashboard, a screen which shows trackers and scripts that are blocked for improved privacy, is the headline feature of Firefox 78. For developers there's quite a lot more on offer.

With its updated RegExp engine, Firefox now supports all new regular expression features introduced in ECMAScript 2018, including the dotAll flag, Unicode property escapes, named capture groups and lookbehind (positive and negative) assertions, which make it possible to find patterns that are (or are not) preceded by another pattern.  In the example below a negative lookbehind is used to match a number only if it is not preceded by a minus sign. A positive lookbehind would match values not preceded by a minus sign:


With regard to WebAssembly, Wasm Multi-value is now supported, meaning that WebAssembly functions can now return multiple values, and instruction sequences can consume and produce multiple stack values. In addition WebAssembly now supports import and export of 64-bit integer function parameters (i64) using BigInt from JavaScript. 

Another enhancement in Firefox 78 that caught my attention is that logpoints, a type of breakpoint that writes a message to the console rather than pausing execution, can now map variable names in source-mapped code back to their original names,  To use this feature and enable the “Map” option in the Debugger’s “Scopes” pane. 

Also, with regard to JavaScript Promises, error logs have become more detailed and now include their name and stack: 


The Accessibility inspector,  a tab in the developer tools that, when enabled, will check a page for accessibility issues is, finally out of beta.

In  Firefox’s pre-release channel, the Developer Edition, there's new functionality to better support async stacks in the Console and Debugger, extending stacks with information about the events, timers, and promises that lead the execution of a specific line of code. It is expected that this features will be enabled across all release channels in Firefox 79.



More Information

New in Firefox 78

A New RegExp Engine in SpiderMonkey

Related Articles

Developer Tool Improvements In Firefox 77

Firefox 69 - New Features But Still Not Caught Up?

Firefox Quantum - Fast For Good

To be informed about new articles on I Programmer, sign up for our weekly newsletter, subscribe to the RSS feed and follow us on Twitter, Facebook or Linkedin.



Raspberry Pi Looks To IPO In London

Raspberry Pi has been changing over the years and the latest upheaval is the proposed IPO. Now we learn that it is likely to be in London and as soon as possible.

GCHQ Celebrates 80 Years Of Colossus

The Colossus computer was created during WWII to decipher critical strategic messages between the most senior German Generals in occupied Europe. To mark it's 80th anniversary GCHQ has relea [ ... ]

More News

raspberry pi books



or email your comment to:





Last Updated ( Friday, 10 July 2020 )