Div to be centered over cursor

I am trying to create a custom cursor using a <div> that is set to follow the cursor.

In the snippet below this is working really well, however when scrolling down the page, the div does not follow until the scroll movement is complete, resulting in a jerky movement and feel.

Is there a way to ensure this doesn't happen and the <div> follows the cursor perfectly regardless?

// vars
var $cursor = $('.custom-cursor');

// Follow cursor
$('body').on('mousemove', function(e) {
  var parentOffset = $(this).offset();
  var relX = e.pageX - parentOffset.left;
  var relY = e.pageY - parentOffset.top;
  $cursor.css({
    left: relX,
    top: relY
  });
});

body {
  background: red;
  height: 1000vh;
  position: relative;
}

.custom-cursor {
  position: absolute;
  width: 30px;
  height: 30px;
  border-radius: 100%;
  z-index: 9999;
  background-color: yellow;
  backface-visibility: hidden;
  pointer-events: none;
  transform: translate(-50%, -50%); // Center over cursor
  transition: width .3s ease-in-out, height .3s ease-in-out;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<body>
  <div class="custom-cursor">
  </div>
</body>

Solution

Insert this code in your code:

$( window ).scroll(function() {
  //Your mouse move function
});

And to get the current position of the mouse on scroll use Get mouse position on scroll.

Here is the link of fiddle http://jsfiddle.net/1byfq24g/ with the implemented code.

// vars
var xMousePos = 0;
var yMousePos = 0;
var lastScrolledLeft = 0;
var lastScrolledTop = 0;
var $cursor = $('.custom-cursor');

// Follow cursor
$('body').on('mousemove', function(e) {
  var parentOffset = $(this).offset();
  var relX = e.pageX - parentOffset.left;
  var relY = e.pageY - parentOffset.top;
  xMousePos = relX;
  yMousePos = relY;

  $cursor.css({
    left: relX,
    top: relY
  });
});
$(window).scroll(function(event) {
  if (lastScrolledLeft != $(document).scrollLeft()) {
    xMousePos -= lastScrolledLeft;
    lastScrolledLeft = $(document).scrollLeft();
    xMousePos += lastScrolledLeft;
  }
  if (lastScrolledTop != $(document).scrollTop()) {
    yMousePos -= lastScrolledTop;
    lastScrolledTop = $(document).scrollTop();
    yMousePos += lastScrolledTop;
  }
  console.log("x = " + xMousePos + " y = " + yMousePos);
  $cursor.css({
    left: xMousePos,
    top: yMousePos
  });
});

body {
  background: red;
  height: 1000vh;
  position: relative;
}

.custom-cursor {
  position: absolute;
  width: 30px;
  height: 30px;
  border-radius: 100%;
  z-index: 9999;
  background-color: yellow;
  backface-visibility: hidden;
  pointer-events: none;
  transform: translate(-50%, -50%); // Center over cursor
  transition: width .3s ease-in-out, height .3s ease-in-out;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js">
</script>

<body>
  <div class="custom-cursor">
  </div>
</body>