ECMAScript 2021

Update 2021-06-22: The 121st Ecma General Assembly approved the ECMAScript 2021 language specification, which means that it’s officially a standard now.

This blog post describes what’s new.

The editors of ECMAScript 2021  #

The editors of this release are:

• Jordan Harband
• Shu-yu Guo
• Michael Ficarra
• Kevin Gibbons

A word on ECMAScript versions  #

Note that since the TC39 process was instituted, the importance of ECMAScript versions has much decreased. What really matters now is what stage a proposed feature is in: Once it has reached stage 4, it can be used safely. But even then, you still have to check if your engines of choice support it.

The features of ES2021 (stage 4 proposals)  #

• String.prototype.replaceAll (Peter Marshall, Jakob Gruber, Mathias Bynens)

• Promise.any() (Mathias Bynens, Kevin Gibbons, Sergey Rubanov)

• WeakRefs (Dean Tribble, Mark Miller, Till Schneidereit, Sathya Gunasekaran, Daniel Ehrenberg) [proposal]

• Logical assignment operators (Justin Ridgewell, Hemanth HM)

• Underscores (_) as separators in number literals and bigint literals (Sam Goto, Rick Waldron)

FAQ  #

What do the stages mean?  #

They refer to maturity stages of the so-called “TC39 process”. Check section “The TC39 process” in “JavaScript for impatient programmers” for more information.

How is [my favorite proposed feature] doing?  #

If you are wondering what stages various proposed features are in, consult the readme of the ECMA-262 GitHub repository.

Is there an official list of ECMAScript features?  #

Yes, the TC39 repo lists finished proposals and mentions in which ECMAScript versions they are introduced.

Free books on ES2021  #

The following books cover JavaScript up to and including ECMAScript 2021 and are free to read online:

• “JavaScript for impatient programmers”
• “Deep JavaScript”