Try to understand more about Javascript -Node.js Async call stack

If I have the following code:

var express = require('express');
var router = express.Router();

/* GET home page. */
router.get('/:name', function(req, res, next) {

  let name = req.params.name;
  setTimeout(()=>{
    res.render('index', { title: name });
  },18000);

});

module.exports = router;

I open the browser and try to request this API many times with different values for name parameter in the sametime, for example:
localhost:3000/param1 , localhost:3000/param2, localhost:3000/param3
Based on the concept of call stack with JavaScript, why name in setTimeOut callback gets the same value of req.params.name with every request. Please check the screenshot.

via Elbassel