2 files changed, 21 insertions, 1 deletions
diff --git a/system/include/emscripten/bind.h b/system/include/emscripten/bind.h
index d70aec91..07955d75 100755
--- a/system/include/emscripten/bind.h
+++ b/system/include/emscripten/bind.h
@@ -713,7 +713,7 @@ namespace emscripten {
     template<typename T>
     class wrapper : public T {
     public:
-        wrapper(const val& wrapped)
+        explicit wrapper(const val& wrapped)
             : wrapped(wrapped)
         {}
 
@@ -722,7 +722,20 @@ namespace emscripten {
             return Caller<ReturnType, Args...>::call(wrapped, name, args...);
         }
 
+        template<typename ReturnType, typename... Args, typename Default>
+        ReturnType optional_call(const char* name, Default def, Args... args) const {
+            if (has_function(name)) {
+                return Caller<ReturnType>::call(wrapped, name);
+            } else {
+                return def();
+            }
+        }
+
     private:
+        bool has_function(const char* name) const {
+            return wrapped.has_function(name);
+        }
+
         // this class only exists because you can't partially specialize function templates
         template<typename ReturnType, typename... Args>
         struct Caller {
diff --git a/system/include/emscripten/val.h b/system/include/emscripten/val.h
index 91f775a7..c27a0fdb 100644
--- a/system/include/emscripten/val.h
+++ b/system/include/emscripten/val.h
@@ -48,6 +48,9 @@ namespace emscripten {
                 unsigned argCount,
                 internal::TYPEID argTypes[]
                 /*, ...*/);
+            bool _emval_has_function(
+                EM_VAL value,
+                const char* methodName);
         }
     }
 
@@ -222,6 +225,10 @@ namespace emscripten {
                 toWireType(args)...);
         }
 
+        bool has_function(const char* name) const {
+            return _emval_has_function(handle, name);
+        }
+
         template<typename T>
         T as() const {
             using namespace internal;