[Web App/Node.js Express] Error Handling

[Basic Error Handling]

// catch 404 and forward to error handler
app.use(function(req, res, next) {
    var err = new Error('Not Found');
    err.status = 404;
    next(err); 
});

[For Error Status - 404]

app.use(function(req, res){
    res.send(404, "404 - Not Found");
});

app.use(function(err, req, res, next){
    res.status(err.status || 404);
    res.end(err.message);
});

[For Error Status - 404 - Result]

[Username - Code]

var app = express();

app.get('/users/:username', function(req, res, next){
    res.send(req.params.username + "'s profile");
});

app.param('username', function(req, res, next, username){
    if(username != 'gchoi') {
        req.user = username;
        next();
    }
    else {
        next(new Error("No User Found"));
    }
});

[Username - Results]