Landing pull request 374. .animate() Callbacks should fire in correct order (unit test included). Fixes #9100.

More Details:
 - https://github.com/jquery/jquery/pull/374
 - https://github.com/jquery/jquery/issues/9100

2 files changed, 18 insertions, 5 deletions

diff --git a/src/effects.js b/src/effects.js
index 88661e0e9..38d5a0119 100644
--- a/src/effects.js
+++ b/src/effects.js
@@ -258,7 +258,6 @@ jQuery.fn.extend({
 			if ( !gotoEnd ) {
 				jQuery._unmark( true, this );
 			}
-			// go in reverse order so anything added to the queue during the loop is ignored
 			while ( i-- ) {
 				if ( timers[i].elem === this ) {
 					if (gotoEnd) {
@@ -522,11 +521,9 @@ jQuery.fx.prototype = {
 
 jQuery.extend( jQuery.fx, {
 	tick: function() {
-		var timers = jQuery.timers,
-			i = timers.length;
-		while ( i-- ) {
+		for ( var timers = jQuery.timers, i = 0 ; i < timers.length ; ++i ) {
 			if ( !timers[i]() ) {
-				timers.splice(i, 1);
+				timers.splice(i--, 1);
 			}
 		}
 
diff --git a/test/unit/effects.js b/test/unit/effects.js
index ea7f4e727..864c4a400 100644
--- a/test/unit/effects.js
+++ b/test/unit/effects.js
@@ -1029,3 +1029,19 @@ test( "animate properties missing px w/ opacity as last (#9074)", 2, function()
 		start();
 	}, 100);
 });
+
+test("callbacks should fire in correct order (#9100)", function() {
+	stop();
+	var a = 1,
+		cb = 0,
+		$lis = jQuery("<p data-operation='*2'></p><p data-operation='^2'></p>").appendTo("#qunit-fixture")
+			// The test will always pass if no properties are animated or if the duration is 0
+			.animate({fontSize: 12}, 13, function() {
+				a *= jQuery(this).data("operation") === "*2" ? 2 : a;
+				cb++;
+				if ( cb === 2 ) {
+					equal( a, 4, "test value has been *2 and _then_ ^2");
+					start();
+				}
+			});
+});