An Express App initializer pattern to tame large apps.
Usually your server.js or app.js is cluttered with a bunch of app.use and app.set middlewares:
var path = require('path'),
exphbs = require('express3-handlebars'),
express = require('express'),
favicon = require('serve-favicon'),
port = process.env.PORT || 3000,
app = express();
// Set the port for easy access
app.set('port', port);
// Set up favicon serving
app.use(favicon('favicon.ico'));
// Set up the handlebars view engine
var hbs = exphbs.create({
layoutsDir: path.join(__dirname, 'views', 'layouts'),
partialsDir: path.join(__dirname, 'views', 'partials'),
defaultLayout: path.join(__dirname, 'views', 'layouts', 'layout.stache'),
extname: '.stache',
// Specify helpers here
helpers: {
foo: function () { return 'FOO!'; },
bar: function () { return 'BAR!'; }
}
});
app.engine('.stache', hbs.engine);
app.set('views', path.join(__dirname, '..', 'views'));
app.set('view engine', '.stache');
/* etc. */
app.listen(app.get('port'), function () {
console.log('Now listening on port ' + app.get('port'));
});This module aims to let you break each individual middleware configuration into their own file for tidier code. Given an example directory structure like this:
├── app.js
├── initializers
│ ├── favicon.js
│ ├── port.js
│ ├── routes.js
│ └── views.jsYour app setup file would look something like this:
var express = require('express'),
initialize = require('express-initializers'),
app = express();
// Let the initializers run
initialize(app)
.then(function () {
// Start listening for requests
app.listen(app.get('port'), function () {
console.log('Now listening on port ' + app.get('port'));
});
})
.catch(function (err) {
console.log('Unable to initialize app: ' + err.message);
console.log(err.stack);
});And each middleware configuration is moved into its own file. From simple examples like port.js:
// initializers/port.js
module.exports = {
configure: function (app) {
app.set('port', process.env.PORT || 3000);
}
};To more complex things like view engines or db initialization:
// initializers/views.js
var path = require('path'),
exphbs = require('express3-handlebars');
module.exports = {
name: 'views',
after: 'static',
configure: function (app) {
// Set up the handlebars view engine
var hbs = exphbs.create({
layoutsDir: path.join(__dirname, 'views', 'layouts'),
partialsDir: path.join(__dirname, 'views', 'partials'),
defaultLayout: path.join(__dirname, 'views', 'layouts', 'layout.stache'),
extname: '.stache',
// Specify helpers here
helpers: {
foo: function () { return 'FOO!'; },
bar: function () { return 'BAR!'; }
}
});
app.engine('.stache', hbs.engine);
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', '.stache');
}
};// initializers/db.js
var db = require('../models/db'),
Promise = require('bluebird');
module.exports = {
configure: function (app) {
return new Promise(function (resolve, reject) {
// Start the db connection
db.init(function (err) {
if (err) {
return reject(new Error('Failed to initialize database: ' + err.message));
}
// Sync all the associations
db.sync(function (err) {
if (err) {
return reject(new Error('Failed to sync database: ' + err.message));
}
app.set('db', db.instance);
resolve();
});
});
});
}
};A more thorough implementation can be seen at node-site.
The initializers function returned from require('express-initializers') can accept options as the second parameter, and an optional callback as the third parameter (if you really hate promises).
initialize(app, {
// Defaults to the 'initializers' directory relative to the calling file
directory: path.join(__dirname, 'configurers'),
// Defaults to '**/*.js'
fileMatch: '**/*.coffee'
}, function (err) {
if (err) {
throw err;
}
app.listen(app.get('port'));
});Each individual initializer must be a module that exports an object of the form:
module.exports = {
name: 'something',
after: 'otherthing',
configure: function (app) {
app.set('something', 42);
}
};The name property can be unique or shared amongst a group of initializers.
The after property allows you to order your initializers, it signals that this initializer should be ran after another or a group of other initializers.
The configure method can optionally return a promise for asynchronous configuration.
MIT License, Copyright 2014 Jacob Gable