const bodyElement = document.querySelector("body");

bodyElement.addEventListener("mousemove", (event) => {
 const x = event.offsetX;
 const y = event.offsetY;
 const spanElement = document.createElement("span");
 spanElement.style.left = x + "px";
 spanElement.style.top = y + "px";
 bodyElement.appendChild(spanElement);
});

browser console showing me this error.

inpage.js:200 
 Uncaught (in promise) 
TypeError: Cannot read properties of null (reading 'type')
    at Di.<anonymous> (inpage.js:200:122709)
    at Generator.next (<anonymous>)
    at Pe (inpage.js:200:121668)

Can’t find where it is coming from.