App VERB

The app.VERB() methods provide the routing functionality in Express, where <strong>VERB</strong> is one of the HTTP verbs, such as app.post(). Multiple callbacks may be given, all are treated equally, and behave just like middleware, with the one exception that these callbacks may invoke next('route') to bypass the remaining route callback(s). This mechanism can be used to perform pre-conditions on a route then pass control to subsequent routes when there is no reason to proceed with the route matched.

The following snippet illustrates the most simple route definition possible. Express translates the path strings to regular expressions, used internally to match incoming requests. Query strings are <em>not</em> considered when peforming these matches, for example "GET /" would match the following route, as would "GET /?name=tobi".

app.get('/', function (req, res) {
  res.send('hello world')
})

Regular expressions may also be used, and can be useful if you have very specific restraints, for example the following would match "GET /commits/71dbb9c" as well as "GET /commits/71dbb9c..4c084f9".

app.get(/^\/commits\/(\w+)(?:\.\.(\w+))?$/, function (req, res) {
  var from = req.params[0]
  var to = req.params[1] || 'HEAD'
  res.send('commit range ' + from + '..' + to)
})

Several callbacks may also be passed, useful for re-using middleware that load resources, perform validations, etc.

app.get('/user/:id', user.load, function () {
  // ...
})

These callbacks may be passed within arrays as well, these arrays are simply flattened when passed:

var middleware = [loadForum, loadThread]

app.get('/forum/:fid/thread/:tid', middleware, function () {
  // ...
})

app.post('/forum/:fid/thread/:tid', middleware, function () {
  // ...
})