Change IS_UNDEFINED to perform value comparison instead on typeof check.

src/macros.py

Index: src/macros.py
diff --git a/src/macros.py b/src/macros.py
index 0b69e6b80e436d477d8a94867d07071bd221101a..d6b700662c0cb04610c2dc84239811d96c1adf2a 100644
--- a/src/macros.py
+++ b/src/macros.py
@@ -97,7 +97,7 @@ const STRING_TO_REGEXP_CACHE_ID = 0;
 #       values of 'bar'.
 macro IS_NULL(arg)              = (arg === null);
 macro IS_NULL_OR_UNDEFINED(arg) = (arg == null);
-macro IS_UNDEFINED(arg)         = (typeof(arg) === 'undefined');
+macro IS_UNDEFINED(arg)         = (arg === (void 0));
 macro IS_NUMBER(arg)            = (typeof(arg) === 'number');
 macro IS_STRING(arg)            = (typeof(arg) === 'string');
 macro IS_BOOLEAN(arg)           = (typeof(arg) === 'boolean');