added two utility functions to emval.

- check if a given key exists.
 - return length of an array.

src/embind/emval.js

@@ -53,6 +53,10 @@ function __emval_new_cstring(str) {
     return __emval_register(Pointer_stringify(str));
 }
 
+function __emval_has_property(handle, k) {
+    return _emval_handle_array[handle].value.hasOwnProperty(k);
+}
+
 function __emval_get_property(handle, k) {
     k = Pointer_stringify(k);
     return __emval_register(_emval_handle_array[handle].value[k]);
@@ -66,6 +70,15 @@ function __emval_get_property_by_unsigned_long(handle, k) {
     return __emval_register(_emval_handle_array[handle].value[k]);
 }
 
+function __emval_get_length(handle) {
+    var val = _emval_handle_array[handle].value;
+    if (Object.prototype.toString.call(val) === "[object Array]") {
+        return val.length;
+    }
+
+    return 0;
+}
+
 function __emval_eval_global_method(handle, objectName, methodName) {
     var objectNameStr = Pointer_stringify(objectName);
     var methodNameStr = Pointer_stringify(methodName);

system/include/emscripten/val.h

@@ -14,12 +14,14 @@ namespace emscripten {
             EM_VAL _emval_new_object();
             EM_VAL _emval_new_long(long value);
             EM_VAL _emval_new_cstring(const char* str);
+            bool _emval_has_property(EM_VAL object, const char* key);
             EM_VAL _emval_get_property(EM_VAL object, const char* key);
             EM_VAL _emval_get_property_by_long(EM_VAL object, long key);
             EM_VAL _emval_get_property_by_unsigned_long(EM_VAL object, unsigned long key);
             EM_VAL _emval_eval_global_method(EM_VAL object, const char* objectName, const char* methodName);
             void _emval_set_property(EM_VAL object, const char* key, EM_VAL value);
             void _emval_set_property_by_int(EM_VAL object, long key, EM_VAL value);
+            unsigned int _emval_get_length(EM_VAL object);
             void _emval_as(EM_VAL value, TYPEID returnType);
             EM_VAL _emval_call(
                 EM_VAL value,
@@ -78,6 +80,10 @@ namespace emscripten {
             return *this;
         }
 
+        bool exist(const char* key) const {
+            return internal::_emval_has_property(handle, key);
+        }
+
         val get(const char* key) const {
             return val(internal::_emval_get_property(handle, key));
         }
@@ -111,6 +117,10 @@ namespace emscripten {
             internal::_emval_set_property_by_int(handle, key, v.handle);
         }
 
+        unsigned int length() {
+            return internal::_emval_get_length(handle);
+        }
+
         template<typename ...Args>
         val operator()(Args... args) {
             using namespace internal;