add redis online user activity tracking example

examples/online/index.js

@@ -0,0 +1,53 @@
+
+// first:
+// npm install redis online
+
+/**
+ * Module dependencies.
+ */
+
+var express = require('../..')
+  , online = require('online')
+  , redis = require('redis')
+  , db = redis.createClient();
+
+// online
+
+online = online(db);
+
+// app
+
+var app = express();
+
+// activity tracking, in this case using
+// the UA string, you would use req.user.id etc
+
+app.use(function(req, res, next){
+  // fire-and-forget
+  online.add(req.headers['user-agent']);
+  next();
+});
+
+/**
+ * List helper.
+ */
+
+function list(ids) {
+  return '<ul>' + ids.map(function(id){
+    return '<li>' + id + '</li>';
+  }).join('') + '</ul>';
+}
+
+/**
+ * GET users online.
+ */
+
+app.get('/', function(req, res, next){
+  online.last(5, function(err, ids){
+    if (err) return next(err);
+    res.send('<p>Users online: ' + ids.length + '</p>' + list(ids));
+  });
+});
+
+app.listen(3000);
+console.log('listening on port 3000');