beat

beat

Simple dependency injection for node

var Beat = require('beat');
var app = new Beat('app');

app.value('port', process.env.PORT || 3000);
app.value('express', require('express'));
  
app.factory('app', function(express){
  return express();
});
  
app.run(function(app, port){
  app.get('/hello.txt', function(req, res){
    res.send('Hello World');
  });
  app.listen(port);
  console.log('Express running at :'+port);
});

How to use

Install it with NPM:

npm install --save beat

Then require it:

var Beat = require('beat');

API

constructor(alias): starts a new Beat with an alias (defaults to "unnamed")

To produce the instance, Beat should be called with new operator.

The alias argument identifies it, useful for debugging in case of errors.

var myServer = new Beat('server');

value(token, value): defines a value for injection

Register the final value.

myServer.value('port', 80);

factory(token, factoryFn): defines a factory for injection

To produce the instance, factoryFn will be called once (with instance context) and its result will be used.

The factoryFn function can use injection annotation.

myServer.factory('port', function(){
  var port = 80;
  // some logic here
  return port;
});

run(fn): runs a code block, with injection

fn will be called (with instance context).

The fn function can use injection annotation.

myServer.run(function(server, port){
  server.listen(port);
});

get(token): obtains a property

myServer.value('port', 80);
var port = myServer.get('port');

load(beatInstance): import properties and factories from an Beat instance

Useful to bind different beats

var config = new Beat('config');
config.value('port', 80);

myServer.load(config);
myServer.run(function(app, port){
  app.listen(port);
});

or at different files

var config = module.exports = new Beat('config');
config.value('port', 80);

myServer.load(require('./config'));
myServer.run(function(app, port){
  app.listen(port);
});

Annotation

Methods run and factory can recieve annotated functions as arguments, that will be used for injection.

The injector looks up tokens based on argument names:

myServer.run(function(server, port) {
  // will inject objects bound to 'server' and 'port' tokens
});

You can also use comments:

myServer.run(function(/* httpServer */ server, /* serverPort */ port) {
  // will inject objects bound to 'http' and 'serverPort' tokens
});

You can also use a array:

myServer.run(['http', 'serverPort', function(server, port) {
  // will inject objects bound to 'http' and 'serverPort' tokens
}]);

Dependencies

Beat instantiation can declare modules as dependencies.

Therefore, declare them as array at constructor second parameter:

var Beat = require('beat');
var db = module.exports = new Beat('db', ['mongoose']);

db.factory('db', function(mongoose, conf) {
  if(conf.env == 'test')
    mongoose.set('debug', true);
  return mongoose.createConnection(conf.mongo).once('open', function() {
    console.log('Mongoose connected');
  });
});

You can also use objects for aliasing:

var Beat = require('beat');
var db = module.exports = new Beat('db', ['mongoose', {conf:'../config.json'}]);

db.factory('db', function(mongoose, conf) {
  if(conf.env == 'test')
    mongoose.set('debug', true);
  return mongoose.createConnection(conf.mongo).once('open', function() {
    console.log('Mongoose connected');
  });
});

file paths starting with / will be relative to process cwd.

If the required module provides a Beat object, their properties will be mixed with local ones:

var Beat = require('beat');
var routes = module.exports = new Beat('routes', [
  '/lib/middlewares',
  '/lib/models',
  '/lib/app'
]);

routes.factory('routes', function routes(app, authMiddleware, ProductsModel){
  app.all('/api/*', authMiddleware);
  app.get('/api/products/:id', function show(req, res) {
    ProductsModel.findById(req.params.id, function(err, doc) {
      res.send(err?400:(doc||404));
    });
  });
});

Is also possible to load dependencies after construction, with the same sintax:

var Beat = require('beat');
var routes = module.exports = new Beat('routes');

routes.loadModules([
  '/lib/middlewares',
  '/lib/models',
  '/lib/app'
]);