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Drupal 11 + jQuery 4: The Slick Carousel Gotcha That Breaks Your Layout

#drupal #drupal11 #wordpress #frontend

import Tabs from '@theme/Tabs';
import TabItem from '@theme/TabItem';

Drupal 11 ships with jQuery 4. jQuery 4 removes $.type(). Slick Carousel uses $.type(). The result is a fatal JavaScript error that kills every carousel on the page. I tracked down the exact failure chain and the fix.

The problem: $.type is no more

🚨 Danger: Breaking Change

When a site running an older Slick Carousel module is upgraded to Drupal 11, the browser console shows: Uncaught TypeError: $.type is not a function. This halts script execution and every Slick carousel on the page fails to initialize.

The failure chain 

flowchart TD
    A[Drupal 11 loads jQuery 4] --> B[Slick Carousel initializes]
    B --> C{Calls $.type}
    C -->|jQuery 3| D[Returns type string]
    C -->|jQuery 4| E[TypeError: $.type is not a function]
    D --> F[Carousel renders]
    E --> G[Script execution halts]
    G --> H[All carousels broken]

    style E fill:#f00,stroke:#333,stroke-width:2px,color:#fff
    style G fill:#f00,stroke:#333,stroke-width:2px,color:#fff
    style H fill:#f00,stroke:#333,stroke-width:2px,color:#fff
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jQuery API removals that affect Drupal contrib

Removed API jQuery 3 jQuery 4 Native replacement
$.type() Works Removed typeof operator
$.isArray() Works Removed Array.isArray()
$.isFunction() Works Removed typeof fn === 'function'
$.isNumeric() Works Removed !isNaN(parseFloat(n))
$.isWindow() Works Removed Manual check

The fix

The Slick Carousel module maintainers patched slick.js to replace $.type() with the native typeof operator. Update to version 3.0.3+ to get the fix.

```javascript title="slick.js (broken on jQuery 4)"
// highlight-next-line
if ( $.type( something ) === 'object' ) {
// ... do object things
}




</TabItem>
<TabItem value="new" label="New slick.js (Compatible)">



```javascript title="slick.js (jQuery 4 safe)" showLineNumbers
// highlight-next-line
if ( typeof something === 'object' ) {
  // ... do object things
}
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The diff:

- if ( $.type( something ) === 'object' ) {
+ if ( typeof something === 'object' ) {
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Update with Composer

```bash title="Terminal"
composer update drupal/slick --with-dependencies




After updating, clear Drupal's caches and test all pages where carousels are used.



```bash title="Terminal"
drush cr
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💡 Tip: Version Check

Always prefer the latest stable release. Version 3.0.3+ contains the jQuery 4 compatibility fix, but later versions may include additional fixes.

Drupal + jQuery compatibility matrix

Drupal Version jQuery Version Slick 2.x Slick 3.0.0-3.0.2 Slick 3.0.3+
Drupal 10.x jQuery 3.x Works Works Works
Drupal 11.x jQuery 4.x Broken Broken Works
Drupal 12.x jQuery 4.x+ Broken Broken Works

Migration checklist

  • [ ] Check current Slick module version: composer show drupal/slick
  • [ ] Update to 3.0.3+: composer update drupal/slick --with-dependencies
  • [ ] Clear Drupal caches: drush cr
  • [ ] Test all pages with carousels
  • [ ] Check browser console for remaining jQuery deprecation warnings
  • [ ] Audit other contrib modules for $.type() usage
  • [x] Verify carousels render correctly on all breakpoints

How to check for other jQuery 4 issues in contrib

Search your project's JavaScript files for removed jQuery APIs:

grep -rn '$.type\|$.isArray\|$.isFunction\|$.isNumeric\|$.isWindow' web/modules/contrib/
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Any matches indicate modules that may break on Drupal 11/jQuery 4.

Why this matters for Drupal and WordPress

Drupal 11 sites using Slick Carousel will hit this jQuery 4 breakage immediately after upgrading. The fix is a Composer update, but teams must also audit other contrib modules for removed jQuery APIs like $.isArray() and $.isFunction(). WordPress themes and plugins that bundle Slick.js face the same issue -- WordPress still ships jQuery 3.x, but themes loading their own jQuery 4 or using jQuery Migrate removal will encounter identical $.type is not a function errors. The grep pattern in this post works for both CMS codebases.

What I learned

  • Upstream dependencies are your dependencies. The Slick Carousel module relies on an external JavaScript library. When a Drupal core dependency (jQuery) changes, it cascades to contributed modules.
  • Proactive maintenance is key. Simply keeping contributed modules up-to-date is the single most effective way to prepare for major Drupal version upgrades. The fix was available long before Drupal 11's release.
  • Consult the issue queue. Before any major upgrade, the Drupal.org issue queue for your key modules is an invaluable resource. A quick search for "Drupal 11" or "jQuery 4" would have highlighted this problem early.

References

Looking for an Architect who doesn't just write code, but builds the AI systems that multiply your team's output? View my enterprise CMS case studies at victorjimenezdev.github.io or connect with me on LinkedIn.

Looking for an Architect who doesn't just write code, but builds the AI systems that multiply your team's output? View my enterprise CMS case studies at victorjimenezdev.github.io or connect with me on LinkedIn.

Originally published at VictorStack AI — Drupal & WordPress Reference

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