// addon.cc
#include 
namespace demo {
using v8::Exception;
using v8::FunctionCallbackInfo;
using v8::Isolate;
using v8::Local;
using v8::Number;
using v8::Object;
using v8::String;
using v8::Value;// This is the implementation of the "add" method// Input arguments are passed using the// const FunctionCallbackInfo& args struct
void Add(const FunctionCallbackInfo& args) {
 Isolate* isolate = args.GetIsolate();
 // Check the number of arguments passed.
 if (args.Length() < 2) {
 // Throw an Error that is passed back to JavaScript
 isolate->ThrowException(Exception::TypeError(
  String::NewFromUtf8(isolate, "Wrong number of arguments")));
 return;
 }
 // Check the argument types
 if (!args[0]->IsNumber() || !args[1]->IsNumber()) {
 isolate->ThrowException(Exception::TypeError(
  String::NewFromUtf8(isolate, "Wrong arguments")));
 return;
 }
 // Perform the operation
 double value = args[0]->NumberValue() + args[1]->NumberValue();
 Local num = Number::New(isolate, value);
 // Set the return value (using the passed in
 // FunctionCallbackInfo&)
 args.GetReturnValue().Set(num);}
void Init(Local