Creating addon in nodejs

Before begining, let me give you a breif idea about some terms

• node-gyp- is a cross-platform command-line tool written in Node.js for compiling native addon modules for Node.js
• NAN- is a thin abstraction layer between the C++ code we write and the Node and V8 APIs

Steps to create your first addon are:-

• Run "npm init" to create package.json in your project root directory

While creating package.json specify your js file as "main": "hello.js"

• (optional) Add a "gypfile": true entry to your package.json so that npm knows this is a binary addon that needs compiling and it needs to invoke node-gyp.
• Install NAN node module in your project root package via "npm install nan@latest --save"
• Create "binding.gyp" describing your source file here it is hello.cc and also define target_name defining the name of your node file i.e. hello.node. In this file, we also define our NAN module.

                    {
                        "targets": [
                            {
                                "target_name": "hello",
                                "sources": [ "hello.cc" ],
                                "include_dirs": [
                                    "<!(node -e \"require('nan')\")"
                                ]
                            }
                        ]
                    }
                

• Write code in hello.cc to print "Hello World"

                    #include <node.h>
                    
                    namespace demo {

                        using v8::FunctionCallbackInfo;
                        using v8::Isolate;
                        using v8::Local;
                        using v8::Object;
                        using v8::String;
                        using v8::Value;
                        
                        void testMethod(const FunctionCallbackInfo<Value>& args) {
                            Isolate* isolate = args.GetIsolate();
                            args.GetReturnValue().Set(String::NewFromUtf8(isolate, "Hello World"));
                        }
                        
                        void init(Local<Object> exports) {
                            NODE_SET_METHOD(exports, "hello", testMethod);
                        }
                        
                        NODE_MODULE(addon, init)
                        
                    }
                

• Compile your addon by running "node-gyp configure". In the ./build/ directory, a Makefile and associated property files will be created. If you don't have gyp install it via "sudo npm install node-gyp -g"
• Next, run "node-gyp build" to start the build process

Alternatively you can use "node-gyp rebuild" to combine the configure and build

The binary output target is called "hello", we will end up with a "hello.node" file either in ./build/Release/ or ./build/Debug/ depending on how node-gyp is invoked and your environment variables.

• Create a file called hello.js with the following contents:

                    var addon = require('./build/Release/hello.node');
                    console.log(addon.hello());
                

Here hello() is the name of funtion you have defined in NODE_SET_METHOD(exports, "hello", testMethod);

In this, the first line is responsible for loading our compiled add-on and pulling in the exports to our module.

• To run the program, simply write "node hello.js" in your project root directory.

Finally to create your first node addon, all you need is

• hello.cc (your C prog)
• building.gyp (Defining targets)
• hello.js (to run your program)

For full documentation, refer to https://nodejs.org/api/addons.html

THANKS