jquery · mgol · Mar 27, 2023 · Mar 13, 2023 · Mar 13, 2023 · Mar 13, 2023
diff --git a/README.md b/README.md
@@ -95,7 +95,6 @@ Some example modules that can be excluded are:
 - **dimensions**: The `.width()` and `.height()` methods, including `inner-` and `outer-` variations.
 - **effects**: The `.animate()` method and its shorthands such as `.slideUp()` or `.hide("slow")`.
 - **event**: The `.on()` and `.off()` methods and all event functionality.
-- **event/focusin**: Cross-browser support for the focusin and focusout events.
 - **event/trigger**: The `.trigger()` and `.triggerHandler()` methods.
 - **offset**: The `.offset()`, `.position()`, `.offsetParent()`, `.scrollLeft()`, and `.scrollTop()` methods.
 - **wrap**: The `.wrap()`, `.wrapAll()`, `.wrapInner()`, and `.unwrap()` methods.

diff --git a/src/event.js b/src/event.js
@@ -27,25 +27,6 @@ function returnFalse() {
 	return false;
 }
 
-// Support: IE <=9 - 11+
-// focus() and blur() are asynchronous, except when they are no-op.
-// So expect focus to be synchronous when the element is already active,
-// and blur to be synchronous when the element is not already active.
-// (focus and blur are always synchronous in other supported browsers,
-// this just defines when we can count on it).
-function expectSync( elem, type ) {
-	return ( elem === safeActiveElement() ) === ( type === "focus" );
-}
-
-// Support: IE <=9 only
-// Accessing document.activeElement can throw unexpectedly
-// https://bugs.jquery.com/ticket/13393
-function safeActiveElement() {
-	try {
-		return document.activeElement;
-	} catch ( err ) { }
-}
-
 function on( elem, types, selector, data, fn, one ) {
 	var origFn, type;
 
@@ -483,7 +464,7 @@ jQuery.event = {
 					el.click && nodeName( el, "input" ) ) {
 
 					// dataPriv.set( el, "click", ... )
-					leverageNative( el, "click", returnTrue );
+					leverageNative( el, "click", true );
 				}
 
 				// Return false to allow normal processing in the caller
@@ -534,10 +515,10 @@ jQuery.event = {
 // synthetic events by interrupting progress until reinvoked in response to
 // *native* events that it fires directly, ensuring that state changes have
 // already occurred before other listeners are invoked.
-function leverageNative( el, type, expectSync ) {
+function leverageNative( el, type, isSetup ) {
 
-	// Missing expectSync indicates a trigger call, which must force setup through jQuery.event.add
-	if ( !expectSync ) {
+	// Missing `isSetup` indicates a trigger call, which must force setup through jQuery.event.add
+	if ( !isSetup ) {
 		if ( dataPriv.get( el, type ) === undefined ) {
 			jQuery.event.add( el, type, returnTrue );
 		}
@@ -549,15 +530,13 @@ function leverageNative( el, type, expectSync ) {
 	jQuery.event.add( el, type, {
 		namespace: false,
 		handler: function( event ) {
-			var notAsync, result,
+			var result,
 				saved = dataPriv.get( this, type );
 
 			if ( ( event.isTrigger & 1 ) && this[ type ] ) {
 
 				// Interrupt processing of the outer synthetic .trigger()ed event
-				// Saved data should be false in such cases, but might be a leftover capture object
-				// from an async native handler (gh-4350)
-				if ( !saved.length ) {
+				if ( !saved ) {
 
 					// Store arguments for use when handling the inner native event
 					// There will always be at least one argument (an event object), so this array
@@ -566,28 +545,17 @@ function leverageNative( el, type, expectSync ) {
 					dataPriv.set( this, type, saved );
 
 					// Trigger the native event and capture its result
-					// Support: IE <=9 - 11+
-					// focus() and blur() are asynchronous
-					notAsync = expectSync( this, type );
 					this[ type ]();
 					result = dataPriv.get( this, type );
-					if ( saved !== result || notAsync ) {
-						dataPriv.set( this, type, false );
-					} else {
-						result = {};
-					}
+					dataPriv.set( this, type, false );
+
 					if ( saved !== result ) {
 
 						// Cancel the outer synthetic event
 						event.stopImmediatePropagation();
 						event.preventDefault();
 
-						// Support: Chrome 86+
-						// In Chrome, if an element having a focusout handler is blurred by
-						// clicking outside of it, it invokes the handler synchronously. If
-						// that handler calls `.remove()` on the element, the data is cleared,
-						// leaving `result` undefined. We need to guard against this.
-						return result && result.value;
+						return result;
 					}
 
 				// If this is an inner synthetic event for an event with a bubbling surrogate
@@ -605,16 +573,11 @@ function leverageNative( el, type, expectSync ) {
 			} else if ( saved.length ) {
 
 				// ...and capture the result
-				dataPriv.set( this, type, {
-					value: jQuery.event.trigger(
-
-						// Support: IE <=9 - 11+
-						// Extend with the prototype to reset the above stopImmediatePropagation()
-						jQuery.extend( saved[ 0 ], jQuery.Event.prototype ),
-						saved.slice( 1 ),
-						this
-					)
-				} );
+				dataPriv.set( this, type, jQuery.event.trigger(
+					saved[ 0 ],
+					saved.slice( 1 ),
+					this
+				) );
 
 				// Abort handling of the native event
 				event.stopImmediatePropagation();
@@ -756,18 +719,73 @@ jQuery.each( {
 }, jQuery.event.addProp );
 
 jQuery.each( { focus: "focusin", blur: "focusout" }, function( type, delegateType ) {
+
+	function focusMappedHandler( nativeEvent ) {
+		if ( document.documentMode ) {
+
+			// Support: IE 11+
+			// Attach a single focusin/focusout handler on the document while someone wants
+			// focus/blur. This is because the former are synchronous in IE while the latter
+			// are async. In other browsers, all those handlers are invoked synchronously.
+
+			// `handle` from private data would already wrap the event, but we need
+			// to change the `type` here.
+			var handle = dataPriv.get( this, "handle" ),
+				event = jQuery.event.fix( nativeEvent );
+			event.type = nativeEvent.type === "focusin" ? "focus" : "blur";
+			event.isSimulated = true;
+
+			// First, handle focusin/focusout
+			handle( nativeEvent );
+
+			// ...then, handle focus/blur
+			//
+			// focus/blur don't bubble while focusin/focusout do; simulate the former by only
+			// invoking the handler at the lower level.
+			if ( event.target === event.currentTarget ) {
+
+				// The setup part calls `leverageNative`, which, in turn, calls
+				// `jQuery.event.add`, so event handle will already have been set
+				// by this point.
+				handle( event );
+			}
+		} else {
+
+			// For non-IE browsers, attach a single capturing handler on the document
+			// while someone wants focusin/focusout.
+			jQuery.event.simulate( delegateType, nativeEvent.target,
+				jQuery.event.fix( nativeEvent ) );
+		}
+	}
+
 	jQuery.event.special[ type ] = {
 
 		// Utilize native event if possible so blur/focus sequence is correct
 		setup: function() {
 
+			var attaches;
+
 			// Claim the first handler
 			// dataPriv.set( this, "focus", ... )
 			// dataPriv.set( this, "blur", ... )
-			leverageNative( this, type, expectSync );
+			leverageNative( this, type, true );
+
+			if ( document.documentMode ) {
 
-			// Return false to allow normal processing in the caller
-			return false;
+				// Support: IE 9 - 11+
+				// We use the same native handler for focusin & focus (and focusout & blur)
+				// so we need to coordinate setup & teardown parts between those events.
+				// Use `delegateType` as the key as `type` is already used by `leverageNative`.
+				attaches = dataPriv.get( this, delegateType );
+				if ( !attaches ) {
+					this.addEventListener( delegateType, focusMappedHandler );
+				}
+				dataPriv.set( this, delegateType, ( attaches || 0 ) + 1 );
+			} else {
+
+				// Return false to allow normal processing in the caller
+				return false;
+			}
 		},
 		trigger: function() {
 
@@ -778,6 +796,24 @@ jQuery.each( { focus: "focusin", blur: "focusout" }, function( type, delegateTyp
 			return true;
 		},
 
+		teardown: function() {
+			var attaches;
+
+			if ( document.documentMode ) {
+				attaches = dataPriv.get( this, delegateType ) - 1;
+				if ( !attaches ) {
+					this.removeEventListener( delegateType, focusMappedHandler );
+					dataPriv.remove( this, delegateType );
+				} else {
+					dataPriv.set( this, delegateType, attaches );
+				}
+			} else {
+
+				// Return false to indicate standard teardown should be applied
+				return false;
+			}
+		},
+
 		// Suppress native focus or blur if we're currently inside
 		// a leveraged native-event stack
 		_default: function( event ) {
@@ -786,6 +822,58 @@ jQuery.each( { focus: "focusin", blur: "focusout" }, function( type, delegateTyp
 
 		delegateType: delegateType
 	};
+
+	// Support: Firefox <=44
+	// Firefox doesn't have focus(in | out) events
+	// Related ticket - https://bugzilla.mozilla.org/show_bug.cgi?id=687787
+	//
+	// Support: Chrome <=48 - 49, Safari <=9.0 - 9.1
+	// focus(in | out) events fire after focus & blur events,
+	// which is spec violation - http://www.w3.org/TR/DOM-Level-3-Events/#events-focusevent-event-order
+	// Related ticket - https://bugs.chromium.org/p/chromium/issues/detail?id=449857
+	//
+	// Support: IE 9 - 11+
+	// To preserve relative focusin/focus & focusout/blur event order guaranteed on the 3.x branch,
+	// attach a single handler for both events in IE.
+	jQuery.event.special[ delegateType ] = {
+		setup: function() {
+
+			// Handle: regular nodes (via `this.ownerDocument`), window
+			// (via `this.document`) & document (via `this`).
+			var doc = this.ownerDocument || this.document || this,
+				dataHolder = document.documentMode ? this : doc,
+				attaches = dataPriv.get( dataHolder, delegateType );
+
+			// Support: IE 9 - 11+
+			// We use the same native handler for focusin & focus (and focusout & blur)
+			// so we need to coordinate setup & teardown parts between those events.
+			// Use `delegateType` as the key as `type` is already used by `leverageNative`.
+			if ( !attaches ) {
+				if ( document.documentMode ) {
+					this.addEventListener( delegateType, focusMappedHandler );
+				} else {
+					doc.addEventListener( type, focusMappedHandler, true );
+				}
+			}
+			dataPriv.set( dataHolder, delegateType, ( attaches || 0 ) + 1 );
+		},
+		teardown: function() {
+			var doc = this.ownerDocument || this.document || this,
+				dataHolder = document.documentMode ? this : doc,
+				attaches = dataPriv.get( dataHolder, delegateType ) - 1;
+
+			if ( !attaches ) {
+				if ( document.documentMode ) {
+					this.removeEventListener( delegateType, focusMappedHandler );
+				} else {
+					doc.removeEventListener( type, focusMappedHandler, true );
+				}
+				dataPriv.remove( dataHolder, delegateType );
+			} else {
+				dataPriv.set( dataHolder, delegateType, attaches );
+			}
+		}
+	};
 } );
 
 // Create mouseenter/leave events using mouseover/out and event-time checks

diff --git a/src/event/focusin.js b/src/event/focusin.js
diff --git a/src/event/support.js b/src/event/support.js
diff --git a/src/jquery.js b/src/jquery.js
@@ -11,7 +11,6 @@ define( [
 	"./queue/delay",
 	"./attributes",
 	"./event",
-	"./event/focusin",
 	"./manipulation",
 	"./manipulation/_evalUrl",
 	"./wrap",