From 602f22c58ba514e8c6436c82ea66f80c2f973d86 Mon Sep 17 00:00:00 2001
From: Kris Kowal <kris.kowal@cixar.com>
Date: Mon, 3 Feb 2014 21:56:59 -0800
Subject: [PATCH] Consider both null and Nan undefined

For the purpose of determining whether a meaningful value exists to
propagate.
---
 observers.js | 2 +-
 operators.js | 4 +++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/observers.js b/observers.js
index 09434b2..2d08534 100644
--- a/observers.js
+++ b/observers.js
@@ -326,7 +326,7 @@ exports.makeDefinedObserver = makeDefinedObserver;
 function makeDefinedObserver(observeValue) {
     return function observeDefault(emit, scope) {
         return observeValue(autoCancelPrevious(function replaceValue(value) {
-            return emit(value != null);
+            return emit(Operators.defined(value));
         }), scope);
     };
 }
diff --git a/operators.js b/operators.js
index 058dfb0..c836872 100644
--- a/operators.js
+++ b/operators.js
@@ -111,7 +111,9 @@ exports.or = function (a, b) {
 };
 
 exports.defined = function (value) {
-    return value != null;
+    // value != null eliminates null and undefined
+    // value === value eliminates NaN
+    return value != null && value === value;
 };
 
 // "startsWith", "endsWith", and "contains"  are overridden in