1192215 - Add docs listing the differences between each of the major ECMAScript versions

Status: RESOLVED WONTFIX

(Developer Documentation Graveyard :: JavaScript, defect, P5)

Description

[Eric Shepherd [:sheppy]]

:: Developer Documentation Request

      Request Type: New Documentation
     Gecko Version: unspecified
 Technical Contact: 

:: Details

Currently, we document what JavaScript features Mozilla has implemented in each release or even in each spec. We should also have docs that generally describe the differences between each of the major ECMAScript specs; this will be useful for developers when trying to decide which JS version to write to, among other things.

Comment 1

[Florian Scholz (Open Web Docs)]

(In reply to Eric Shepherd [:sheppy] from comment #0)
> will be useful for developers when trying to decide which JS version to
> write to, among other things.

There is only one JS version, really. See the 1JS movement and bug 867609. What varies is *support* for different JS features. ECMAScript is moving towards a yearly release or living standard like HTML, making the "version" even more irrelevant.

In practise, no web dev really has to make decisions on ECMAScript versions, but looks at feature support in browsers or node etc. Especially now that we live in a world of transpilers like babel.

Our doc strategy for this is a bit different: On each feature reference pages, we include a specification table. It has a comment column where incompatibilities and changes between the specs for this specific feature can be mentioned. Also, if a change in behaviour really impacts web developers, we document this change on the feature reference page, as it often comes to our radar via dev-doc-needed. This way the information is directly there when people use the feature and read it up, and not hidden in a list of hundreds of things that are tied to a (for them not important) ES spec version.

And the specs itself already list incompatibilities with prior versions (which is a lot of work already for the spec writers).
ES5 to prior: http://www.ecma-international.org/ecma-262/5.1/#sec-E
ES6 to prior: http://www.ecma-international.org/ecma-262/6.0/#sec-additions-and-changes-that-introduce-incompatibilities-with-prior-editions

We do already have pages that list the features that are introduced in each spec and mention the Firefox version there as well. The one for ES6 is quite large, but now that there are yearly releases it will be much shorter and even less relevant (cf. HTML5 and HTML5.1)
https://developer.mozilla.org/en-US/docs/Web/JavaScript/New_in_JavaScript/ECMAScript_6_support_in_Mozilla

All that said, I am not sure it is worth the enormous amount of work that is involved here (mainly collecting all the information, sorting it, explaining, ...)

Leaning towards WONTFIX. What do you think?

Comment 2

[Eric Shepherd [:sheppy]]

(In reply to Florian Scholz [:fscholz] (MDN) from comment #1)

> Leaning towards WONTFIX. What do you think?

Agreed. This was something I filed by someone's suggestion, and it sounded like a good idea at the time, but really wasn't. :)