Here is the form and addingTask() function.
<form method="GET" action="/newtask" onsubmit="addingTask()">
  <label> Today's Task: </label><br>
  <input type="text" id="task"><br>
  <button type="submit">Add</button>
</form>
<script>
  function addingTask() {
    var data = {
      task: $("#task").val(),
    }
    $.ajax({
      type: "GET",
      url: "/newtask",
      dataType: 'JSON',
      data: data,
      success: function success(result) {
        console.log("iiiiiiiiiiiii", result);
        console.log("565656565656565");
      },
      error: function error(error) {
        console.log("sdsdsdsdsd", error);
        console.log("mmmmnnnnmmmnnn");
      }
    })
  }
</script>

   This is the route file.
   var express = require('express');
   var router = express.Router();
   const indexController = 
   require("../controllers/indexController");

   /* GET home page. */
   router.get('/', function(req, res, next) {
   res.render('index', { title: 'To-Do-List' });
   });

   router.get('/newtask', indexController.createTask
   );

   module.exports = router;

   This is the controller function file.
   
   const createTask = (req, res, next) => {
   console.log(req.body);
   var variable = JSON.stringify(req.body);
   res.render('index', { title: variable });
   };

   module.exports = {          //A module means file
   createTask
   }

Initial Screen https://i.stack.imgur.com/itWPX.png

After filling the form and on clicking the add button i get empty title https://i.stack.imgur.com/AqIWf.png

I have tried changing http method to 'POST' but still the same error occurs.