Implementing callbacks

In keeping with the typical pattern of a Node program, add-ons also implement the notion of callbacks. As one might expect in a Node program, a C++ add-on performing an expensive and time-consuming operation should comprehend the notion of asynchronously executing functions.

The following code will expose a method that will pass back the current system time to any callback it is sent:

#include <node.h>
#include <ctime>

using namespace v8;

Handle<Value> GetTime(const Arguments& args) {
  HandleScope scope;

  Local<Function> cb = Local<Function>::Cast(args[0]);
  const unsigned argc = 1;
  time_t stamp = time(0);
  Local<Value> argv[argc] = { 
    Local<Value>::New(Number::New(stamp)) 
  };
  cb->Call(Context::GetCurrent()->Global(), argc, argv);

  return scope.Close(Undefined());
}

void Init(Handle<Object> exports, Handle<Object> module) {
  module->Set(String::NewSymbol("exports"),FunctionTemplate...