[wp-trac] [WordPress Trac] #18022: Author dropdown on post.php hangs in IE if number of usernames is large

[WordPress Trac]

#18022: Author dropdown on post.php hangs in IE if number of usernames is large
----------------------------+-----------------------------
 Reporter:  dbvista         |      Owner:
     Type:  defect (bug)    |     Status:  new
 Priority:  normal          |  Milestone:  Awaiting Review
Component:  Administration  |    Version:  3.1
 Severity:  normal          |   Keywords:
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 When I visit wp-admin/posts.php to post a new article in Internet Explorer
 8, and click the '''Author''' dropdown to try to change the author, and
 the dropdown contains ''many usernames'' (say, 1000), the dropdown does
 not open and the entire web page hangs. (This does not happen in Firefox.)
 After several seconds, IE displays this error dialog:

 ''Stop running this script?
 A script on this page is causing Internet Explorer to run slowly. If it
 continues to run, your computer may become unresponsive.''

 Dismissing the dialog makes the web page come back to life; however, the
 dropdown does not open.

 If you reduce the number of usernames in the dropdown, the problem goes
 away. This suggests that WordPress JavaScript is running very slowly,
 proportional to the number of usernames.

 You may be tempted to think this is a Microsoft or IE problem, but here
 some evidence that it's a WordPress problem:

 1. I created a plain HTML page with a 5000-item dropdown, and the same IE
 browser displayed it immediately without any delay. This suggests the
 problem is unique to WordPress.

 2. The problem does not occur in Firefox (3.6.18). This suggests that
 WordPress has an IE-specific performance problem in some JavaScript code.

 3. Possible clue: If I remove the following line from wp-admin/admin-
 header.php, the problem disappears. This suggests WordPress is adding some
 kind of JavaScript processing to this dropdown that is slowing it down.

 {{{
 ajaxurl = '<?php echo admin_url('admin-ajax.php'); ?>',
 }}}

 Deactivating all plugins and changing theme to Twenty Ten does not affect
 the problem.

 I posted about this in the forums first:
 http://wordpress.org/support/topic/author-dropdown-on-postphp-displays-ie-
 error-stop-running-this-script

 Other people have reported this problem in version 3.2:
 http://wordpress.org/support/topic/cannot-edit-change-author-when-editing-
 blog-posts-with-word-press-324

 I am happy to participate in solving this by running tests you come up
 with.

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Ticket URL: <http://core.trac.wordpress.org/ticket/18022>
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