NodeJS & C++ with Node-Addon-Api

Node-Addon-Api - NodeJS - node-gyp

About

Here is a small tutorial to use c++ with NodeJs!

I'll show you how to create a small C++ addon, with Napi that allows binding.

We will use node-gyp to compile everything.

Installation on Windows

1. Install Visual Studio Tools

   • Select Desktop Environment C++ and Click on install

2. Install Python3.10

3. Execute Windows Power Shell in Administrator

(If you watch this tutorial I assume you have already installed NodeJS and Npm otherwise do it)

Enter his commands :

npm install -g node-gyp

npm config set python python3.10

npm config set msvs_version 2017

Set-ExecutionPolicy Unrestricted -Force

Create your First project

1. You can now go or create your folder that will contain your project

On the terminal enter :

npm init

It's up to you to fill in with the right arguments... Then enter

npm install -S node-addon-api

2. Create a folder at the root of your project that will contain your C++ module

   • Create name_module.cpp It will contain your script that nodeJs will use
   • Create name_module.h It will contain the header / declaration of your functions and constant of your file name_module.cpp
   • Create index.cpp It will contain the script to link between c++ and nodeJs

3. Create a file binding.gyp at the root

Write inside

{
  "targets": [
    {
      "target_name": "nameModule",
      "cflags!": [ "-fno-exceptions" ],
      "cflags_cc!": [ "-fno-exceptions" ],
      "sources": [
        "./folder_contain_module/name_module.cpp",
        "./folder_contain_module/index.cpp"
      ],
      "include_dirs": [
        "<!@(node -p \"require('node-addon-api').include\")"
      ],
      'defines': [ 'NAPI_DISABLE_CPP_EXCEPTIONS' ],
    }
  ]
}

• target_name : is the .node name that will be returned when compiling

• sources : is the location of each .cpp file to compile

• include_dirs : the script will retrieve the node-addon-api content to compile correctly

• Others : mandatory files to have no problem

  4. Create your First C++ script

We of course we create a Hello World function

I advise you to rename your files like this, to understand better :

name_module.cpp -> hello.cpp

name_module.h -> hello.h

Folder : helloWorld

In the binding.gyp, write:

{
  "targets": [
    {
      "target_name": "helloModule",
      "cflags!": [ "-fno-exceptions" ],
      "cflags_cc!": [ "-fno-exceptions" ],
      "sources": [
        "./helloWorld/hello.cpp",
        "./helloWorld/index.cpp"
      ],
      "include_dirs": [
        "<!@(node -p \"require('node-addon-api').include\")"
      ],
      'defines': [ 'NAPI_DISABLE_CPP_EXCEPTIONS' ],
    }
  ]
}

In hello.cpp write :

#include <string>
#include "hello.h"

std::string helloWorld() {
  return "Hello World !!!";
}

In hello.h write :

#include <string>

std::string helloWorld();
}

In index.cpp write :

#include <napi.h>
#include <string>
#include "hello.h" //get the header of your function

Napi::String helloWorldFonc(const Napi::CallbackInfo& info) { //create a new function who recovers the argument with Callback
    Napi::Env env = info.Env();
    std::string result = helloWorld(); //your function -> hello.cpp
    return Napi::String::New(env, result);
}
Napi::Object Init(Napi::Env env, Napi::Object exports) { //Object to export your script on nodeJs
    exports.Set(
        Napi::String::New(env, "helloWorld"), // function name for nodeJs (const hello = require('./helloModule.node').helloWorld();
        Napi::Function::New(env, helloWorldFonc) //the fonction create just before with callBack
    );
    return exports;
}
NODE_API_MODULE(helloModule, Init) //out name.node (the same as in "binding.gyp") and Init == exports

The script is finished, not very complicated... All that's left is to compile it into .node

On your terminal, write :

node-gyp configure and node-gyp build

Get the file generate .node in /Build/Release/helloModule.node and drag it to the root

Use it on your index.js file !!!

const myAddon = require('./helloModule.node');
console.log(myAddon.helloWorld());

Launch your file then admire the work 😎

Use arguments on this function

In hello.cpp write :

#include <string>
#include "hello.h"

std::string helloWorld( std::string Argument ) {
  return "Hello" + Argument + " !!!";
}

In hello.h write :

#include <string>

std::string helloWorld( std::string Argument );
}

In index.cpp write :

#include <napi.h>
#include <string>
#include "hello.h"

Napi::String helloWorldFonc(const Napi::CallbackInfo& info) { // the arguments are stored here!!!
    Napi::Env env = info.Env();
    std::string Argument = (std::string) info[0].ToString(); // get the first argument
    std::string result = helloWorld(Argument);
    return Napi::String::New(env, result);
}
Napi::Object Init(Napi::Env env, Napi::Object exports) {
    exports.Set(
        Napi::String::New(env, "helloWorld"),
        Napi::Function::New(env, helloWorldFonc)
    );
    return exports;
}
NODE_API_MODULE(helloModule, Init)

Don't forget to delete the Buildfolder and rebuild with node-gyp

In index.js

const myAddon = require('./helloModule.node');
console.log(myAddon.helloWorld('everyone'));

And that's magic

Here I hope to have helped you...

Other basic scripts are available on git, do not hesitate to look at them 🧐

Contact

Discord : WaRtrO#6293