Update wp_register_script documentation to recommend registration on init instead of wp_enqueue_scripts

[jhned]

I disagree with ​this part of the documentation for wp_register_script:

The function should be called using the wp_enqueue_scripts action hook if you want to call it on the front-end of the site. To call it on the administration screens, use the admin_enqueue_scripts action hook. For the login screen, use the login_enqueue_scripts action hook. Calling it outside of an action hook can often lead to unexpected results and should be avoided.

First off, according to _wp_scripts_maybe_doing_it_wrong, init is also an acceptable hook for registering scripts. The benefit we get from registering scripts on init is that plugins can get a comprehensive list of the registered scripts and styles in the WordPress Admin by accessing the "registered" property of the $wp_scripts and $wp_styles globals. If we're going to register scripts and styles, we should be able to pull a full list of the registered scripts and styles. The recommended usage is only for code efficiency, and has no other useful aspect to it.

[Otto42]

The init action happens before the *_enqueue_scripts hooks, so you will not get a "comprehensive" list at that point in time. Any scripts that are enqueue-ing on the recommended hooks will not be registered or listed at the init hook time.

The reason for waiting until *_enqueue_scripts is that it is the last point in the process when a script can be added before wp_print_scripts outputs them (in the header). Waiting until the last possible moment has the advantage of having everything relevant probably loaded by that point.

[Otto42]

Additionally, comments can be left on the documentation there, or brought up to the #docs team directly. Meta trac isn't really the right place for these.

Since you have left a comment on that page already, I'll close this.

[jhned]

Thanks for the clarification, I'll continue the discussion with #docs.