Major

User pain Issue Created
75% details#1797438: HTML5 validation is preventing form submit and not fully accessible 2012-09-28
64% details#1870006: HTML5 validation with table sticky header is misaligned over the toolbar 2012-12-19
60% details#2235977: JS Client-side file validation is broken (because ajaxPageState is broken?) 2014-07-11
60% details#2624496: "Edit summary" button broken if text area with a summary has description 2015-11-27
60% details#2725255: Unfiltered data in "Allowed HTML tags" 2016-05-14
57% details#2258313: Implement JS Web License Labels to allow for JS minification 2014-05-05
57% details#2316205: Provide a way to disable animations for a11y 2014-08-06
54% details#736066: ajax.js insert command sometimes wraps content in a div, potentially producing invalid HTML and other bugs 2010-03-09
54% details#1988968: Drupal.ajax does not guarantee that "add new JS file to page" commands have finished before calling said JS 2013-05-08
54% details#2493957: Add back errors & summary support to native HTML5 details tag 2015-05-23
51% details#2666746: [PERFORMANCE] Simultaneous file uploads re-posting data 2016-02-11
45% details#2725259: [regression] Table Drag handles no longer respond to up/down arrow keys 2016-05-14
43% details#2141055: When multiple instances of the same entity on one page, only the first can be edited 2013-11-21
43% details#2412945: Determine which additional asset libraries should be in the critical path/loaded i/t header (core/drupal, core/dropbutton) 2015-01-23
43% details#2705327: Failed to execute 'contains' on 'Node' 2016-04-13
43% details#2856047: Avoid random failures in JavascriptTestBase when testing functionality in a dialog 2017-02-26
43% details#2880703: Status report page without JavaScript is messed up 2017-05-23
43% details#2909128: Autocomplete intermittent on Chrome Android 2017-09-15
39% details#2343351: Make picture polyfill optional 2014-09-23
34% details#2315773: Create a menu link field type/widget/formatter 2014-08-05
34% details#2346973: Replace jQuery UI autocomplete with Select2 2014-09-30
34% details#2423093: Allow multiple target entity types in the 'entity_autocomplete' Form API element 2015-02-11
34% details#2554221: Port Cross-site Scripting - Autocomplete system from SA-CORE-2015-003 to Drupal 8 2015-08-20
34% details#2570093: Replace !placeholder with @placeholder where needed in JavaScript 2015-09-17
34% details#2784935: Use Backbone for client-side state management 2016-08-16
34% details#2815199: Add tools and scripts for writing and running javascript unit tests 2016-10-08
34% details#2828528: Add Quick Edit Functional JS test coverage 2016-11-17
34% details#2863444: Discourage/make impossible to select a "to" date that is before the "from" date 2017-03-23
34% details#2878620: Update AirBnB Coding standards to most recent major versions 2017-05-15
34% details#2898533: Better define the backwards compatibility/API policy for JavaScript 2017-07-31
34% details#2899055: Update Babel transpile targets to match Drupal supported versions 2017-08-01
34% details#2899141: jQuery Form Plugin update to latest stable release 2017-08-01
34% details#2908864: Update CKEditor library to 4.7.3 2017-09-14
30% details#2395453: Allow client-side caching to be disabled while developing 2014-12-18
29% details#2764931: Contextual links don't work with 'use-ajax' links 2016-07-12
29% details#2901667: To optimize outside_in Drupal.behaviors.toggleEditMode 2017-08-12
26% details#1945262: Replace custom weights with dependencies in library declarations; introduce "before" and "after" for conditional… 2013-03-17
26% details#2334403: Addition and deletion of shortcuts should not reload the page 2014-09-11
26% details#2413847: Remove .js class from core 2015-01-25
26% details#2527740: Consider to remove support for #ajax['url'] 2015-07-06
26% details#2560457: Support drag-and-drop image uploads in CKEditor 2015-08-31
23% details#2822932: Make Settings Tray candidates and actively edited items more visually obvious 2016-10-28
23% details#2905922: Implementation issue for Layout Builder 2017-08-31
23% details#2910705: Update JS Build Script Packages 2017-09-22
21% details#1203766: With large number of permissions /admin/people/permissions becomes unusable 2011-06-29
21% details#2082319: Comment's node_new_comments View field history markers ("new" comment marker) forces render caching to be per user 2013-09-05
17% details#2899363: Provide an interface for JavaScript tests to capture browser console messages 2017-08-02
14% details#2119299: Make sure D8 works with mobile proxy browsers 2013-10-24
14% details#2620748: Recoverable fatal error: Argument 1 passed to Drupal\comment\CommentManager::getCountNewComments() 2015-11-22
11% details#1090592: [meta] Use HTML5 data-drupal-* attributes instead of #ID selectors in Drupal.settings 2011-03-12
11% details#2082317: Forum history markers ("new" and "updated" markers, "x new posts" links) forces render caching to be per user 2013-09-05
11% details#2513356: Add a default CSP and clickjacking defence and minimal API for CSP to core 2015-06-27
11% details#2651660: Investigate where and how a frontend framework could be used 2016-01-17
9% details#2465749: [meta] Widespread HTML validation issue - The ID attribute MUST be unique on the page. 2015-04-05
9% details#2885090: JS Roadmap for 8.4 2017-06-10
6% details#2645250: [META] Start using reactive declarative JS programming for some new core admin UIs 2016-01-06
4% details#1787222: [meta] Strategy for updating vendor JS libraries within a major stable version 2012-10-12
4% details#2490140: [Meta] Make sure contrib use ESLint 2015-05-17

Sorting of the JavaScript issue queues based on user pain rating.

User pain = Type * Priority * Public / Max score

Highlighted rows are killer issues , issues that take a significant effort to fix due to their complexity.