I am new to Javascript, so pardon me my trivial mistakes. I have written the following script in which `res` is supposed to be a Global variable in the script file. I am setting the global `res` in a method and then accessing it in another method, however the issue is, `this.issue` returns `undefined` in method Y but it isn't undefined in the method X where I assign a value to it. Why is that?

**Method X is called before Method Y.**

```
var res;

/* GET home page. */
router.get('/', function(req, res, next) {
  res.render('index', { title: 'Express', shortenedUrl: ''});
});

router.X('/yolo', jsonParser, function(req, res, next) {
    this.res = res;
    console.log("this.res: "+ this.res); // this.res not undefined here
    Y();
});

function Y(){
    console.log("this.res: "+ this.res); // this.res here becomes undefined
});

```