As a newcomer to nodejs, I've been delving into some code and trying to grasp its concepts. Could someone kindly guide me in understanding the following code snippets? My inquiries might be basic, but please note that I'm on a learning curve with nodejs and express, striving to decipher existing code. The code lines are numbered for reference to corresponding questions.
var ChatApp = global.ChatApp = {}
, conf = ChatApp.conf = require('./conf').config (1)
, http = require('http') (2)
, path = require('path') (3)
, express = require('express')
, app = express()
;
app.set('views', __dirname + '/views');
app.set('view engine', 'jade');
app.use(express.logger('dev')); (6)
app.use(express.bodyParser()); (7)
app.use(express.methodOverride()); (8)
app.use(express.cookieParser('your secret here')); (9)
app.use(express.session({secret: 'PTKACSxSq24PlZ9IAPRMy3_2'})); (10)
app.all('*', function(req, res, next) {
var oneof = false;
if(req.headers.origin) {
res.header('Access-Control-Allow-Origin', req.headers.origin);
oneof = true;
}
if(req.headers['access-control-request-method']) {
res.header('Access-Control-Allow-Methods', req.headers['access-control-request-method']);
oneof = true;
}
if(req.headers['access-control-request-headers']) {
res.header('Access-Control-Allow-Headers', req.headers['access-control-request-headers']);
oneof = true;
}
if(oneof) {
res.header('Access-Control-Max-Age', 60 * 60 * 24 * 365);
} (11)
// intercept OPTIONS method
if (oneof && req.method == 'OPTIONS') {
res.send(200);
}
else {
next();
}
}); (12)
app.use(app.router); (13)
app.use(express.static(path.join(__dirname, 'public')));
if ('development' == app.get('env')) {
app.use(express.errorHandler());
} (15)
server = http.createServer(app); (16)
require('./lib/chat').init(server); (17)
(1) Regarding
conf = ChatApp.conf = require('./conf').config(2),(3) Why are we requiring http and path modules with require(http) and require(path)? What roles do these two serve?
(6) In app.use(express.logger('dev')), the parameter 'dev' perplexes me. Is it a path of sorts?
(7) How does app.use(express.bodyParser()) actually parse request bodies with JSON, urlencoded, and multipart support as mentioned on the Express website?
(8) The purpose and usage of
app.use(express.methodOverride())(9) While express.cookieparser parses the cookie header field, what exactly constitutes a header field in a cookie?
(10) A mysterious method called express.session() has left me puzzled. Can you shed light on its functionality?
(12) Code fragment 12's objective eludes me. What's the intention behind it?
(13) Calling app.use(app.router) led to this output when logged:
function router(req, res, next){
self._dispatch(req, res, next);
}(15) Running app.get.env returned 'development' sourced from a file within express/lib/application.js. But why conduct this test?
(16) I'm confused by utilizing http.createServer(app) despite already declaring var server = http.createServer() alongside var app = express(). Can you explain this redundancy?
(17) Within the lib/chat folder in my app root, there's an index.js file along with other files. Should we include only the index.js or all JS files in the folder? And what's the significance of initializing the server in this context?
I'd greatly appreciate any guidance on these queries.