[wp-trac] [WordPress Trac] #60647: Script Modules: Allow modules to depend on existing WordPress scripts

[WordPress Trac]

#60647: Script Modules: Allow modules to depend on existing WordPress scripts
-----------------------------+------------------------------
 Reporter:  jonsurrell       |       Owner:  jonsurrell
     Type:  feature request  |      Status:  assigned
 Priority:  normal           |   Milestone:  Awaiting Review
Component:  Script Loader    |     Version:  trunk
 Severity:  normal           |  Resolution:
 Keywords:                   |     Focuses:  javascript
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Comment (by jonsurrell):

 One concern with the proxy module approach was around the ordering of
 script execution. For example, the proposed proxy module `@wordpress/a11y`
 has an implicit dependency on the `wp-a11y` script. `wp-a11y` exposes
 required global variables and therefore ''must be executed before''
 `@wordpress/a11y`.

 I've done some testing and research and it appears that the ordering of
 scripts printed on the page will not be a problem. In summary, if the
 scripts are not `async` or `defer` (by default they are not), and modules
 are not `async` (by default they are not), they will executed in the order
 we require.

 -----

 Enqueued scripts are printed as `script` tags without `async` or `defer`
 attributes. [https://developer.mozilla.org/en-
 US/docs/Web/HTML/Element/script#notes This means they "are fetched and
 executed immediately before the browser continues to parse the page."]
 **Enqueued scripts will be fetched and executed in the order they appear
 on the page.**

 Modules (`<script type="module">`) [https://developer.mozilla.org/en-
 US/docs/Web/HTML/Element/script#defer are always treated as `defer`, which
 means:]

 > the script is meant to be executed after the document has been parsed.

 If we put those together, we can see that scripts are executed before
 parsing continues, while modules are executed after the document has been
 parsed. This ordering means that modules can depend on scripts
 independently of where the ordering of script tags on the page.

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/60647#comment:5>
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