added content-negotiation example

examples/content-negotiation/app.js

@@ -0,0 +1,47 @@
+
+/**
+ * Module dependencies.
+ */
+
+var express = require('../../lib/express');
+
+var app = express.createServer();
+
+var users = [
+    { name: 'tobi' }
+  , { name: 'loki' }
+  , { name: 'jane' }
+];
+
+function provides(type) {
+  return function(req, res, next){
+    if (req.accepts(type)) return next();
+    next('route');
+  }
+}
+
+// curl http://localhost:3000/users -H "Accept: application/json"
+
+app.get('/users', provides('json'), function(req, res){
+  res.send(users);
+});
+
+// curl http://localhost:3000/users -H "Accept: text/html"
+
+app.get('/users', provides('html'), function(req, res){
+  res.send('<ul>' + users.map(function(user){
+    return '<li>' + user.name + '</li>';
+  }).join('\n') + '</ul>');
+});
+
+// curl http://localhost:3000/users -H "Accept: text/plain"
+
+app.get('/users', function(req, res, next){
+  res.contentType('txt');
+  res.send(users.map(function(user){
+    return user.name;
+  }).join(', '));
+});
+
+app.listen(3000);
+console.log('Express server listening on port 3000');