optimized _.eq function, remove redundant comparison when both null

underscore.js

@@ -1185,7 +1185,7 @@
     // See the [Harmony `egal` proposal](http://wiki.ecmascript.org/doku.php?id=harmony:egal).
     if (a === b) return a !== 0 || 1 / a === 1 / b;
     // A strict comparison is necessary because `null == undefined`.
-    if (a == null || b == null) return a === b;
+    if (a == null || b == null) return false;
     // `NaN`s are equivalent, but non-reflexive.
     if (a !== a) return b !== b;
     // Exhaust primitive checks