Fix TypeError when Bootstrap is included in `head` (#32024)

* extend jquery after domContentLoaded event is fired

* add unittest for util onDOMContentLoaded

* wait for trigger jquery event after domContentLoaded

* remove domcontentready from eventHandler

* move istanbul ignore statements to correct line

Co-authored-by: XhmikosR <[email protected]>

1 files changed, 14 insertions, 11 deletions

diff --git a/js/src/dropdown.js b/js/src/dropdown.js
index 28d8b7299..46311ee8a 100644
--- a/js/src/dropdown.js
+++ b/js/src/dropdown.js
@@ -7,6 +7,7 @@
 
 import {
   getjQuery,
+  onDOMContentLoaded,
   getElementFromSelector,
   isElement,
   isVisible,
@@ -512,23 +513,25 @@ EventHandler.on(document, EVENT_CLICK_DATA_API, SELECTOR_DATA_TOGGLE, function (
 })
 EventHandler.on(document, EVENT_CLICK_DATA_API, SELECTOR_FORM_CHILD, e => e.stopPropagation())
 
-const $ = getjQuery()
-
 /**
  * ------------------------------------------------------------------------
  * jQuery
  * ------------------------------------------------------------------------
  * add .dropdown to jQuery only if jQuery is present
  */
-/* istanbul ignore if */
-if ($) {
-  const JQUERY_NO_CONFLICT = $.fn[NAME]
-  $.fn[NAME] = Dropdown.jQueryInterface
-  $.fn[NAME].Constructor = Dropdown
-  $.fn[NAME].noConflict = () => {
-    $.fn[NAME] = JQUERY_NO_CONFLICT
-    return Dropdown.jQueryInterface
+
+onDOMContentLoaded(() => {
+  const $ = getjQuery()
+  /* istanbul ignore if */
+  if ($) {
+    const JQUERY_NO_CONFLICT = $.fn[NAME]
+    $.fn[NAME] = Dropdown.jQueryInterface
+    $.fn[NAME].Constructor = Dropdown
+    $.fn[NAME].noConflict = () => {
+      $.fn[NAME] = JQUERY_NO_CONFLICT
+      return Dropdown.jQueryInterface
+    }
   }
-}
+})
 
 export default Dropdown