From bf3aa97c3614f032983afe0740813021e70a06dd Mon Sep 17 00:00:00 2001
From: Michael Ficarra <git@michael.ficarra.me>
Date: Sun, 4 Sep 2011 19:34:19 -0400
Subject: [PATCH] reverting some changes to isEqual that were a little too
 aggressive

---
 test/objects.js |  4 ++--
 underscore.js   | 17 ++++++++++-------
 2 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/test/objects.js b/test/objects.js
index 4234f0fad..bb0f98553 100644
--- a/test/objects.js
+++ b/test/objects.js
@@ -72,8 +72,8 @@ $(document).ready(function() {
 
     var moe   = {name : 'moe', lucky : [13, 27, 34]};
     var clone = {name : 'moe', lucky : [13, 27, 34]};
-	var isEqualObj = {isEqual: function (o) { return o.isEqual == this.isEqual; }, unique: {}};
-	var isEqualObjClone = {isEqual: isEqualObj.isEqual, unique: {}};
+    var isEqualObj = {isEqual: function (o) { return o.isEqual == this.isEqual; }, unique: {}};
+    var isEqualObjClone = {isEqual: isEqualObj.isEqual, unique: {}};
     ok(moe != clone, 'basic equality between objects is false');
     ok(_.isEqual(moe, clone), 'deep equality is true');
     ok(_(moe).isEqual(clone), 'OO-style deep equality works');
diff --git a/underscore.js b/underscore.js
index 3ad38311b..7615b5d5e 100644
--- a/underscore.js
+++ b/underscore.js
@@ -610,14 +610,16 @@
     // `NaN` values are equal.
     if (_.isNaN(a)) return _.isNaN(b);
     // Compare dates by their millisecond values.
-    if (_.isDate(a)) return _.isDate(b) && a.getTime() == b.getTime();
+    var isDateA = _.isDate(a), isDateB = _.isDate(b);
+    if (isDateA || isDateB) return isDateA && isDateB && a.getTime() == b.getTime();
     // Compare RegExps by their source patterns and flags.
-    if (_.isRegExp(a))
-      return _.isRegExp(b) &&
-        a.source == b.source &&
-        a.global == b.global &&
-        a.multiline == b.multiline &&
-        a.ignoreCase == b.ignoreCase;
+    var isRegExpA = _.isRegExp(a), isRegExpB = _.isRegExp(b);
+    if (isRegExpA || isRegExpB)
+        return isRegExpA && isRegExpB &&
+            a.source == b.source &&
+            a.global == b.global &&
+            a.multiline == b.multiline &&
+            a.ignoreCase == b.ignoreCase;
     // Ensure that both values are objects.
     if (typeA != 'object') return false;
     // Unwrap any wrapped objects.
@@ -625,6 +627,7 @@
     if (b._chain) b = b._wrapped;
     // Invoke a custom `isEqual` method if one is provided.
     if (typeof a.isEqual == 'function') return a.isEqual(b);
+    if (typeof b.isEqual == 'function') return b.isEqual(a);
     // Compare array lengths to determine if a deep comparison is necessary.
     if ('length' in a && (a.length !== b.length)) return false;
     // Assume equality for cyclic structures.