N-API

Introduction#

The N-API is a new and better way for creating native module for NodeJS. N-API is in early stage so it may have inconsistent documentation.

Hello to N-API

This module register hello function on hello module. hello function prints Hello world on console with printf and return 1373 from native function into javascript caller.

#include <node_api.h>
#include <stdio.h>


napi_value say_hello(napi_env env, napi_callback_info info)
{
    napi_value retval;

    printf("Hello world\n");

    napi_create_number(env, 1373, &retval);

    return retval;
}

void init(napi_env env, napi_value exports, napi_value module, void* priv)
{
    napi_status status;
    napi_property_descriptor desc = {
        /*
         * String describing the key for the property, encoded as UTF8.
         */
        .utf8name = "hello",
        /*
         * Set this to make the property descriptor object's value property
         * to be a JavaScript function represented by method.
         * If this is passed in, set value, getter and setter to NULL (since these members won't be used).
         */
        .method = say_hello,
        /*
         * A function to call when a get access of the property is performed.
         * If this is passed in, set value and method to NULL (since these members won't be used).
         * The given function is called implicitly by the runtime when the property is accessed
         * from JavaScript code (or if a get on the property is performed using a N-API call).
         */
        .getter = NULL,
        /*
         * A function to call when a set access of the property is performed.
         * If this is passed in, set value and method to NULL (since these members won't be used).
         * The given function is called implicitly by the runtime when the property is set
         * from JavaScript code (or if a set on the property is performed using a N-API call).
         */
        .setter = NULL,
        /*
         * The value that's retrieved by a get access of the property if the property is a data property.
         * If this is passed in, set getter, setter, method and data to NULL (since these members won't be used).
         */
        .value = NULL,
        /*
         * The attributes associated with the particular property. See napi_property_attributes.
         */
        .attributes = napi_default,
        /*
         * The callback data passed into method, getter and setter if this function is invoked.
         */
        .data = NULL
    };
    /*
     * This method allows the efficient definition of multiple properties on a given object.
     */
    status = napi_define_properties(env, exports, 1, &desc);

    if (status != napi_ok)
        return;
}


NAPI_MODULE(hello, init)