Interface Application

app.disabled('foo') // => true

app.enable('foo') app.disabled('foo') // => false

app.enabled('foo') // => false

app.enable('foo') app.enabled('foo') // => true

By default will require() the engine based on the file extension. For example if you try to render a "foo.jade" file Express will invoke the following internally:

app.engine('jade', require('jade').__express);

For engines that do not provide .__express out of the box, or if you wish to "map" a different extension to the template engine you may use this method. For example mapping the EJS template engine to ".html" files:

app.engine('html', require('ejs').renderFile);

In this case EJS provides a .renderFile() method with the same signature that Express expects: (path, options, callback), though note that it aliases this method as ejs.__express internally so if you're using ".ejs" extensions you dont need to do anything.

Some template engines do not follow this convention, the Consolidate.js library was created to map all of node's popular template engines to follow this convention, thus allowing them to work seamlessly within Express.

• setup default configuration
• setup default middleware
• setup route reflection methods

A node http.Server is returned, with this application (which is a Function) as its callback. If you wish to create both an HTTP and HTTPS server you may do so with the "http" and "https" modules as shown here:

var http = require('http') , https = require('https') , express = require('express') , app = express();

http.createServer(app).listen(80); https.createServer({ ... }, app).listen(443);

NOTE: Sub-apps will:

• Not inherit the value of settings that have a default value. You must set the value in the sub-app.
• Inherit the value of settings with no default value.

Parameter mapping is used to provide pre-conditions to routes which use normalized placeholders. For example a :user_id parameter could automatically load a user's information from the database without any additional code,

The callback uses the samesignature as middleware, the only differencing being that the value of the placeholder is passed, in this case the id of the user. Once the next() function is invoked, just like middleware it will continue on to execute the route, or subsequent parameter functions.

 app.param('user_id', function(req, res, next, id){
   User.find(id, function(err, user){
     if (err) {
       next(err);
     } else if (user) {
       req.user = user;
       next();
     } else {
       next(new Error('failed to load user'));
     }
   });
 });

For example if the application was mounted as "/admin", which itself was mounted as "/blog" then the return value would be "/blog/admin".

Example:

app.render('email', { name: 'Tobi' }, function(err, html){ // ... })

app.set('foo', 'bar'); app.get('foo'); // => "bar" app.set('foo', ['bar', 'baz']); app.get('foo'); // => ["bar", "baz"]

Mounted servers inherit their parent server's settings.