[jsinterp] Extend function regex (closes #86)

pytube/jsinterp.py

@@ -231,7 +231,7 @@ class JSInterpreter(object):
     def extract_function(self, funcname):
         func_m = re.search(
             r'''(?x)
-                (?:function\s+%s|[{;]%s\s*=\s*function|var\s+%s\s*=\s*function)\s*
+                (?:function\s+%s|[{;,]%s\s*=\s*function|var\s+%s\s*=\s*function)\s*
                 \((?P<args>[^)]*)\)\s*
                 \{(?P<code>[^}]+)\}''' % (
                 re.escape(funcname), re.escape(funcname), re.escape(funcname)),