From 76c5237cc408c01ae67f5c68d39ed6f1e4ef8003 Mon Sep 17 00:00:00 2001
From: Richard Gibson <richard.gibson@gmail.com>
Date: Mon, 1 Aug 2016 14:20:38 -0400
Subject: [PATCH] Event: Optimize delegated event processing

Closes gh-3255
---
 src/event.js | 41 ++++++++++++++++++++++++-----------------
 1 file changed, 24 insertions(+), 17 deletions(-)

diff --git a/src/event.js b/src/event.js
index b3fa59de5..859f99e08 100644
--- a/src/event.js
+++ b/src/event.js
@@ -355,51 +355,58 @@ jQuery.event = {
 	},
 
 	handlers: function( event, handlers ) {
-		var i, matches, sel, handleObj,
+		var i, handleObj, sel, matchedHandlers, matchedSelectors,
 			handlerQueue = [],
 			delegateCount = handlers.delegateCount,
 			cur = event.target;
 
-		// Support: IE <=9
 		// Find delegate handlers
-		// Black-hole SVG <use> instance trees (#13180)
-		//
-		// Support: Firefox <=42
-		// Avoid non-left-click in FF but don't block IE radio events (#3861, gh-2343)
-		if ( delegateCount && cur.nodeType &&
-			( event.type !== "click" || isNaN( event.button ) || event.button < 1 ) ) {
+		if ( delegateCount &&
+
+			// Support: IE <=9
+			// Black-hole SVG <use> instance trees (trac-13180)
+			cur.nodeType &&
+
+			// Support: Firefox <=42
+			// Suppress spec-violating clicks indicating a non-primary pointer button (trac-3861)
+			// https://www.w3.org/TR/DOM-Level-3-Events/#event-type-click
+			// Support: IE 11 only
+			// ...but not arrow key "clicks" of radio inputs, which can have `button` -1 (gh-2343)
+			!( event.type === "click" && event.button >= 1 ) ) {
 
 			for ( ; cur !== this; cur = cur.parentNode || this ) {
 
 				// Don't check non-elements (#13208)
 				// Don't process clicks on disabled elements (#6911, #8165, #11382, #11764)
-				if ( cur.nodeType === 1 && ( cur.disabled !== true || event.type !== "click" ) ) {
-					matches = [];
+				if ( cur.nodeType === 1 && !( event.type === "click" && cur.disabled === true ) ) {
+					matchedHandlers = [];
+					matchedSelectors = {};
 					for ( i = 0; i < delegateCount; i++ ) {
 						handleObj = handlers[ i ];
 
 						// Don't conflict with Object.prototype properties (#13203)
 						sel = handleObj.selector + " ";
 
-						if ( matches[ sel ] === undefined ) {
-							matches[ sel ] = handleObj.needsContext ?
+						if ( matchedSelectors[ sel ] === undefined ) {
+							matchedSelectors[ sel ] = handleObj.needsContext ?
 								jQuery( sel, this ).index( cur ) > -1 :
 								jQuery.find( sel, this, null, [ cur ] ).length;
 						}
-						if ( matches[ sel ] ) {
-							matches.push( handleObj );
+						if ( matchedSelectors[ sel ] ) {
+							matchedHandlers.push( handleObj );
 						}
 					}
-					if ( matches.length ) {
-						handlerQueue.push( { elem: cur, handlers: matches } );
+					if ( matchedHandlers.length ) {
+						handlerQueue.push( { elem: cur, handlers: matchedHandlers } );
 					}
 				}
 			}
 		}
 
 		// Add the remaining (directly-bound) handlers
+		cur = this;
 		if ( delegateCount < handlers.length ) {
-			handlerQueue.push( { elem: this, handlers: handlers.slice( delegateCount ) } );
+			handlerQueue.push( { elem: cur, handlers: handlers.slice( delegateCount ) } );
 		}
 
 		return handlerQueue;
-- 
2.39.5