private static JavaScriptValue RunScript(JavaScriptValue callee, bool isConstructCall, JavaScriptValue[] arguments, ushort argumentCount, IntPtr callbackData)
        {
            if (argumentCount < 2)
            {
                ThrowException("not enough arguments");
                return JavaScriptValue.Invalid;
            }

            //
            // Convert filename.
            //

            string filename = arguments[1].ToString();

            //
            // Load the script from the disk.
            //

            string script = File.ReadAllText(filename);
            if (string.IsNullOrEmpty(script))
            {
                ThrowException("invalid script");
                return JavaScriptValue.Invalid;
            }

            //
            // Run the script.
            //

            return JavaScriptContext.RunScript(script, currentSourceContext++, filename);
        }

        public string init()
        {
            JavaScriptContext context;

            if (Native.JsCreateRuntime(JavaScriptRuntimeAttributes.None, null, out runtime) != JavaScriptErrorCode.NoError)
                return "failed to create runtime.";

            if (Native.JsCreateContext(runtime, out context) != JavaScriptErrorCode.NoError)
                return "failed to create execution context.";

            if (Native.JsSetCurrentContext(context) != JavaScriptErrorCode.NoError)
                return "failed to set current context.";

            // ES6 Promise callback
            JavaScriptPromiseContinuationCallback promiseContinuationCallback = delegate (JavaScriptValue task, IntPtr callbackState)
            {
                promiseCallback = task;
            };

            if (Native.JsSetPromiseContinuationCallback(promiseContinuationCallback, IntPtr.Zero) != JavaScriptErrorCode.NoError)
                return "failed to setup callback for ES6 Promise";

            if (Native.JsProjectWinRTNamespace("Windows") != JavaScriptErrorCode.NoError)
                return "failed to project windows namespace.";

            if (Native.JsStartDebugging() != JavaScriptErrorCode.NoError)
                return "failed to start debugging.";

            return "NoError";
        }

        private static JavaScriptValue Echo(JavaScriptValue callee, bool isConstructCall, JavaScriptValue[] arguments, ushort argumentCount, IntPtr callbackData)
        {
            for (uint index = 1; index < argumentCount; index++)
            {
                if (index > 1)
                {
                    Console.Write(" ");
                }

                Console.Write(arguments[index].ConvertToString().ToString());
            }

            Console.WriteLine();

            return JavaScriptValue.Invalid;
        }

        private static void DefineHostCallback(JavaScriptValue globalObject, string callbackName, JavaScriptNativeFunction callback, IntPtr callbackData)
        {
            //
            // Get property ID.
            //

            JavaScriptPropertyId propertyId = JavaScriptPropertyId.FromString(callbackName);

            //
            // Create a function
            //

            JavaScriptValue function = JavaScriptValue.CreateFunction(callback, callbackData);

            //
            // Set the property
            //

            globalObject.SetProperty(propertyId, function, true);
        }

 internal static extern JavaScriptErrorCode JsGetContextOfObject(JavaScriptValue obj, out JavaScriptContext context);

 internal static extern JavaScriptErrorCode JsInstanceOf(JavaScriptValue obj, JavaScriptValue constructor, out bool result);

 internal static extern JavaScriptErrorCode JsGetIndexedPropertiesExternalData(JavaScriptValue obj, IntPtr data, out JavaScriptTypedArrayType arrayType, out uint elementLength);

 internal static extern JavaScriptErrorCode JsGetOwnPropertySymbols(JavaScriptValue obj, out JavaScriptValue propertySymbols);

 internal static extern JavaScriptErrorCode JsGetSymbolFromPropertyId(JavaScriptPropertyId propertyId, out JavaScriptValue symbol);

 internal static extern JavaScriptErrorCode JsGetDataViewStorage(JavaScriptValue dataView, out byte[] buffer, out uint bufferLength);

 internal static extern JavaScriptErrorCode JsGetAndClearException(out JavaScriptValue exception);

 internal static extern JavaScriptErrorCode JsCreateURIError(JavaScriptValue message, out JavaScriptValue error);

 internal static extern JavaScriptErrorCode JsCreateFunction(JavaScriptNativeFunction nativeFunction, IntPtr externalData, out JavaScriptValue function);

 internal static extern JavaScriptErrorCode JsConstructObject(JavaScriptValue function, JavaScriptValue[] arguments, ushort argumentCount, out JavaScriptValue result);

 internal static extern JavaScriptErrorCode JsCallFunction(JavaScriptValue function, JavaScriptValue[] arguments, ushort argumentCount, out JavaScriptValue result);

 internal static extern JavaScriptErrorCode JsGetArrayBufferStorage(JavaScriptValue arrayBuffer, out byte[] buffer, out uint bufferLength);

 internal static extern JavaScriptErrorCode JsGetTypedArrayStorage(JavaScriptValue typedArray, out byte[] buffer, out uint bufferLength, out JavaScriptTypedArrayType arrayType, out int elementSize);

 internal static extern JavaScriptErrorCode JsSetException(JavaScriptValue exception);

 internal static extern JavaScriptErrorCode JsCreateSymbol(JavaScriptValue description, out JavaScriptValue symbol);

 internal static extern JavaScriptErrorCode JsSetObjectBeforeCollectCallback(JavaScriptValue reference, IntPtr callbackState, JavaScriptObjectBeforeCollectCallback beforeCollectCallback);