Node.JS callback function, listen input object event

Following is a standard Node.js http get request. In the callback function, we listen response 'data' and 'end' event.

My question is: what if the response data event fired before the callback execution? It seems possible to me.

var request = http.get(option, function(res) {
            res.setEncoding('utf8');
            var data = "";
            res.on('data', function(d) {
                data += d
            });

            res.on('end', function() {
                ...
            });
        });