Using app.configure in express

I found some code where they set up Express without using app.configure and I was wondering, what's the difference between using app.configure without an environment specifier and not using it?

In other words, what's the difference between this:

var app = require(express);

app.configure(function(){
    app.set('port', process.env.PORT || config.port);
    app.use(express.logger('dev'));  /* 'default', 'short', 'tiny', 'dev' */
    app.use(express.bodyParser());
    app.use(express.static(path.join(__dirname, 'site')));
}

and this:

var app = require(express);

app.set('port', process.env.PORT || config.port);
app.use(express.logger('dev'));  /* 'default', 'short', 'tiny', 'dev' */
app.use(express.bodyParser());
app.use(express.static(path.join(__dirname, 'site')));

Thanks.

It is optional and remain for legacy reason, according to the doc. In your example, the two piece of codes have no difference at all. http://expressjs.com/api.html#app.configure

Update 2015:

@IlanFrumer points out that app.configure is removed in Express 4.x. If you followed some outdated tutorials and wondering why it didn't work, You should remove app.configure(function(){ ... }. Like this:

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

app.use(...);
app.use(...);

app.get('/', function (req, res) {
    ...
});