getting arguments in c++ from nodejs

Question

I'm trying to build nthRoot function in c++ and then embed it in my node js project.

the problem is all the tutorials that are on the web are for an old v8 version and don't work in node 12+

I'm not a c++ programmer

#include <node.h>
#include <iostream>


using namespace v8;
using namespace std;


double NthRoot(const FunctionCallbackInfo<Value>& args) {
    Isolate* isolate = args.GetIsolate();
   int n = args[0]->IntegerValue();
   double degree = args[1]->DoubleValue();

   double result =   std::pow(n, 1.0/degree);

   args.GetReturnValue().Set(result);

}

void Initialize(Local<Object> exports) {
   NODE_SET_METHOD(exports, "nthroot", NthRoot);
}

NODE_MODULE(addon, Initialize);

I'd recommend using the [N-API](https://nodejs.org/api/n-api.html) or even [node-addon-api](https://github.com/nodejs/node-addon-api) rather than v8. [is-floating-point-math-broken](https://stackoverflow.com/questions/588004/is-floating-point-math-broken) may also be relevant — Alan Birtles, Nov 23 '20 at 08:20
It is true that Napi and node-addon-api are better solutions, but generally someone would like to use directly V8. In this case how should anyone do in order to get the args of a function? — EuberDeveloper, Jan 18 '22 at 01:09

score 0 · Answer 1 · answered Nov 23 '20 at 10:38

ended up using napi


#include <napi.h>

Napi::Value NthRoot(const Napi::CallbackInfo& info) {
  Napi::Env env = info.Env();

  if (info.Length() < 2) {
    Napi::TypeError::New(env, "Wrong number of arguments")
        .ThrowAsJavaScriptException();
    return env.Null();
  }

  if (!info[0].IsNumber() || !info[1].IsNumber()) {
    Napi::TypeError::New(env, "Wrong arguments").ThrowAsJavaScriptException();
    return env.Null();
  }

  double arg0 = info[0].As<Napi::Number>().DoubleValue();
  double arg1 = info[1].As<Napi::Number>().DoubleValue();
  Napi::Number num = Napi::Number::New(env, pow(arg0,1.0/arg1));

  return num;
}

Napi::Object Init(Napi::Env env, Napi::Object exports) {
  exports.Set(Napi::String::New(env, "nthroot"), Napi::Function::New(env, NthRoot));
  return exports;
}

NODE_API_MODULE(cMath, Init)

score 0 · Answer 2 · answered Jan 18 '22 at 01:13

Even if using Napi is generally better, that does not answer the original question

I think I found some documentation to do it:

// addon.cc
#include <node.h>

using namespace v8;

void Add(const FunctionCallbackInfo<Value>& args) {
  Isolate* isolate = Isolate::GetCurrent();
  HandleScope scope(isolate);

  if (args.Length() < 2) {
    isolate->ThrowException(Exception::TypeError(
        String::NewFromUtf8(isolate, "Wrong number of arguments")));
    return;
  }

  if (!args[0]->IsNumber() || !args[1]->IsNumber()) {
    isolate->ThrowException(Exception::TypeError(
        String::NewFromUtf8(isolate, "Wrong arguments")));
    return;
  }

  double value = args[0]->NumberValue() + args[1]->NumberValue();
  Local<Number> num = Number::New(isolate, value);

  args.GetReturnValue().Set(num);
}

void Init(Handle<Object> exports) {
  NODE_SET_METHOD(exports, "add", Add);
}

NODE_MODULE(addon, Init)

Where the documentation is here: https://node.readthedocs.io/en/latest/api/addons/

getting arguments in c++ from nodejs

2 Answers2