Any news about the `<module>` element?

Domenic Denicola d at
Sat Dec 20 12:14:09 PST 2014

I think the only reason `require` was used is to draw your attention to the module resolution algorithm used in Node, and not at all to imply anything about the semantics.

From: es-discuss [mailto:es-discuss-bounces at] On Behalf Of John Barton
Sent: Saturday, December 20, 2014 15:02
To: Matthew Robb
Cc: es-discuss list
Subject: Re: Any news about the `<module>` element?

On Sat, Dec 20, 2014 at 10:54 AM, Matthew Robb <matthewwrobb at<mailto:matthewwrobb at>> wrote:

On Sat, Dec 20, 2014 at 1:50 PM, Caridy Patino <caridy at<mailto:caridy at>> wrote:
what make you think this proposal implies blocking?

​I think he was reading your examples using "require()" and thinking you were suggesting that the semantics would match.​

Indeed that is what I was thinking.

A non-blocking <module> tag is a poor match to HTML, a declarative language where order of tags means order of parsing and rendering. Giving up this fundamental characteristic of HTML, in the long-shot effort to improve the apparent load time for some amateur Web sites, has become dogmatic so I suppose there is no value in discussing it.

A non-blocking <module> tag would also prevent experienced developers from controlling rendering through JS action. That means they will need to use <script> tags which we'd like to deprecate or we'd have to have a blocking form of <module>.  We'll probably end up with the latter choice.

On the node side, require() is curiously synchronous given node's heavy emphasis on asynchronous IO. As with the browser <script> tag, the synchronous require() is the best choice for simplicity.  But the synchronous semantics prevents optimizations on both platforms. An asynchronous root-module loading API in a next generation system opens new opportunities.  I hope and expect we'll end up with an async option on node.

On balance I think a non-blocking <module> tag with optional blocking is reasonable.

However, the description of the browser loading as "require()" within a asynchronous <module> tag is really a complete departure from all the previous discussions.  A system based on require() is not statically analyzable. I could go on, but really a shift to this extreme seems so unlikely that there must be some misunderstanding.  Rather I assume that the content of the <module> tag will be ES6 code as we know it now and that we will have an additional dynamic loading API that will be asynchronous much like we had earlier this year.  Exactly the same solution would work in node.

In other words, <script> and require() would not be used in future code, an async API would be available for root loading, and most developers most of the time would write synchronous code manipulating modules contents.  If we are not heading in this direction I hope there will be more discussions in public.

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