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Adrian Sandu
Adrian Sandu

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ES2021 candidate, Edge Legacy end of support, Polypane 5, and Safari Technology Preview 122 | Front End News #021

NOTE: This is issue #021 of my newsletter, which went live on Monday, March 15th. If you find this information useful and interesting and you want to receive future issues as they are published, ahead of everyone else, I invite you to join the subscriber list at

It has been an important week for JavaScript as the final feature set of ECMAScript 2021 was decided. Next, we have even more browser news: Edge Legacy will no longer receive any security updates, Polypane released version 5 with a lot of new features, and Safari Technology Preview 122 is now available. Some of the major releases of the week include d3 v6.6.0, Karma v6.2.0, and Socket.IO 4.0.0.

Get ready for ECMAScript 2021

ECMAScript 2021 (or ES2021) is the latest set of updates for JavaScript, and it just reached candidate status. This iteration contains all the proposals that have reached stage 4:

  • String.prototype.replaceAll
  • Promise.any()
  • WeakRefs
  • Logical assignment operators
  • Underscores (_) as separators in number literals and bigint literals

For more details, you can check Dr. Axel Rauschmayer's coverage of these upcoming features. And if you enjoy reading documentation, you can review the full official specifications.

Browser news


There will be no more security updates for Microsoft Edge Legacy. The desktop application will be replaced with the new version as part of the April Windows 10 monthly security update. If you are using this application in any way, you should check the following article for more details.


Polypane, the browser for responsive web development, has been updated to version 5. It includes Chrome 89, and it boasts performance improvements, better UI elements, and new debugging tools. Here are just a few of these updates:

  • support for aspect-ratio and @scroll-timeline (due to Chromium 89)
  • you can follow the tab order with Focus Order Overview
  • a new tool to disable images and background images

The complete list of changes is available in the official release notes linked below.


Safari Technology Preview 122 is now available for download. Here are just a few of the updates packed in this version:

  • support for :focus-visible
  • experimental support for CSS Color 5 features
  • better support for aspect-ratio
  • support for private, private static methods in JavaScript

Follow the link below for the release notes.

Software updates and Releases

  • acorn v8.1.0 - small, fast, JavaScript-based JavaScript parser
  • d3 v6.6.0 - Bring data to life with SVG, Canvas and HTML
  • esbuild v0.9.0 - an extremely fast JavaScript bundler and minifier
  • Hybrids v5.0.0 - the simplest way to create web components from plain objects and pure functions.
  • Karma v6.2.0 - test runner for JavaScript
  • Socket.IO 4.0.0 - realtime application framework (Node.JS server)

Wrapping things up

That's all I have prepared for this issue. Have a great and productive week, keep yourselves safe, and I will see you next time!

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