Dependency Injection for nodejs

In software engineering, dependency injection is a technique whereby one object (or static method) supplies the dependencies of another object. A dependency is an object that can be used (a service).

After to use several nodejs frameworks, my eyes were damaged with a thousands of require("...") and new("...")

I researched and I can not find anything compared with java spring framework for dependency injection.

So... :D

Usage

Without D.I

index.js

var express = require('express');
var app = express();

app.get('/', function(req, res) {
  res.type('text/plain');
  res.send('Hell , its about time!!');
});

app.get('/another', function(req, res) {
  res.type('text/plain');
  res.send('Hell , one more time!!');
});

app.listen(process.env.PORT || 8080);

With D.I

index.js

const path = require('path');
const express = require('express');
const di4nodejs = require('dependency-injection-4nodejs').DependencyInjection;
var app = express();
di4nodejs.discover(path.resolve(__dirname), "index.js", app);
app.listen(process.env.PORT || 8080);

Routes.js

//@Dependency("Routes")
function Routes() {
  var _this = this;

  //@Autowire
  var express;
  this.main = function() {
    _this.express.get('/', function(req, res) {
      res.type('text/plain');
      res.send('Hell , its about time!!');
    });

    _this.express.get('/another', function(req, res) {
      res.type('text/plain');
      res.send('Hell , one more time!!');
    });
  }
}
module.exports = Routes;

As you can see, express was autowired.

If you need to use another module inside, Routes.js, just autowire it

Logger.js

//@Dependency("Logger")
function Logger() {
  var _this = this;

  this.main = function() {
    // logger configurations
  }
}
module.exports = Logger;

Routes.js

//@Dependency("Routes")
function Routes() {
  var _this = this;

  //@Autowire
  var express;

  //@Autowire
  var logger;

  this.main = function() {
    _this.express.get('/', function(req, res) {
      _this.logger.info("first endpoint");
      res.type('text/plain');
      res.send('Hell , its about time!!');
    });

    _this.express.get('/another', function(req, res) {
      _this.logger.info("second endpoint");
      res.type('text/plain');
      res.send('Hell , one more time!!');
    });
  }
}
module.exports = Routes;

Copyright

• Home image : https://www.freecodecamp.org/news/a-quick-intro-to-dependency-injection-what-it-is-and-when-to-use-it-7578c84fa88f/

Coming soon

• Tests
• Documentation
• Register as npm dependency