Underscore 0.4.4, with isNumber, isString, and isEqual(NaN, NaN)

underscore.js

@@ -31,7 +31,7 @@
   if (typeof exports !== 'undefined') exports._ = _;
 
   // Current version.
-  _.VERSION = '0.4.3';
+  _.VERSION = '0.4.4';
 
   /*------------------------ Collection Functions: ---------------------------*/
 
@@ -399,6 +399,8 @@
     if (a == b) return true;
     // One of them implements an isEqual()?
     if (a.isEqual) return a.isEqual(b);
+    // Both are NaN?
+    if (_.isNumber(a) && _.isNumber(b) && isNaN(a) && isNaN(b)) return true;
     // If a is not an object by this point, we can't handle it.
     if (atype !== 'object') return false;
     // Nothing else worked, deep compare the contents.
@@ -430,6 +432,16 @@
     return Object.prototype.toString.call(obj) == '[object Function]';
   };
 
+  // Is a given value a String?
+  _.isString = function(obj) {
+    return Object.prototype.toString.call(obj) == '[object String]';
+  };
+
+  // Is a given value a Number?
+  _.isNumber = function(obj) {
+    return Object.prototype.toString.call(obj) == '[object Number]';
+  };
+
   // Is a given variable undefined?
   _.isUndefined = function(obj) {
     return typeof obj == 'undefined';