NodeJS: My node files have dependencies on variables in an other file

问题

I am creating an app with nodejs. In the app, I have a app.js script that is the entrypoint that initializes both the app, as an expressjs app, and the http server that I use.

Just to clarify: modules here are not npm modules, they are my own files. I've written the app in modules. They are just seperate script files used by require()-ing them.

This app has several modules that a main module handler initializes. It reads the contents of a folder, which contains my own modules, and then by convention call the .initialize on each module after running a require() call on the filenames without the .js extension.

However, I have 1 module that needs the app variable to create an endpoint, and 1 module that needs the httpServer variable to create a web socket. Both of these are instansiated in app.js.

Seeing as I don't know what kind of modules will be in the folder, I don't really want to send app and httpServer to every module if they are just needed by 1 module each. Something like dependency injection would fit nice, but is that possible without to much overhead?

Right now I just temporarily added app and httpServer to the GLOBAL object.

回答1:

What I usually do is have app.js export app so that modules elsewhere in my app can require it directly rather than having to deal with passing it around everywhere. I also slightly modify app.js so that it won't "listen" if it is required as a module that way later on if i decide to wrap it with another app, I can with minimal changes. This is not important to your question, I just find it give me more control when unit testing. All you really need from the code below is module.exports = app

'use strict';
var express = require('express'),
  app = express(),
  config = require('config'),
  pkg = require('./package.json');

// trust reverse proxies
app.enable('trust proxy');

app.set('version', pkg.version);
module.exports = app; // <--- *** important ***

if (app.get('env') !== 'production') {
  app.set('debug', true);
}

// calling app.boot bootstraps the app
app.boot = function (skipStart) { // skipStart var makes it easy to unit test without actually starting the server
  // add middleware
  require('./middleware/');

  // setup models
  app.set('models', require('./models'));

  // setup routes
  require('./routes/');

  // wait for a dbconnection to start listening
  app.on('dbopen', function () {

    // setup hosting params
    if (!skipStart) {
      let server = app.listen(config.port, function () {
        app.emit('started');
        console.log('Web Server listening at: http://%s:%s', server.address().address, server.address().port);

        // mail server interceptor for dev
        if (app.get('env') !== 'production') { 
          // Config smtp server for dev
          let SMTPServer = require('smtp-server').SMTPServer,
            mailServer = new SMTPServer({
              secure: false,
              disabledCommands: ['STARTTLS'],
              onData: function(stream, session, callback){
                stream.pipe(process.stdout); // print message to console
                stream.on('end', callback);
              },
              onAuth: function (auth, session, callback) {
                callback(null, {user: 1, data: {}});
              }
            });
          // Start smtp server
          mailServer.listen(1025, '0.0.0.0');
        } else {
          // start agenda jobs only on production
          require('./jobs.js');
          console.log('Agenda Jobs Running.');
        }
      });
    } else {
      app.emit('booted');
    }
  });
};

// If this is the main module, run boot.
if (require.main === module) {
  // move all of this to next tick so we can require app.js in other modules safely.
  process.nextTick(app.boot);
}

回答2:

Suppose you want to initialize 2 file from main app.js

app.js

var socketIni = require('./socketini.js');//You have to pass server
var xyz  = require('./xyz.js')//you have to pass app
var app = express();
var server=http.createServer(app);
socketIni(server);
xyz(app);

socketini.js

module.exports = function(server){
   //your socket initilize  goes here
  var io = require('socket.io').listen(server);
}

xyz.js

 module.exports = function(app){
   //you can access app here
 }

来源：https://stackoverflow.com/questions/31477523/nodejs-my-node-files-have-dependencies-on-variables-in-an-other-file

标签

javascript

node.js

express

dependencies