JSFiddle - React, Tailwind, and code Playground

HTML

<div id="x_div"></div>
 <div id="y_div"></div>

CSS

body{ margin:0; padding:0; font-family:Arial, Helvetica, sans-serif; font-size:12px; background-color:#ececec;}
 #x_div, #y_div { position:absolute; top:0;left:0; background-color:blue; width:100%; height:2px; }
 #y_div { height:100%; width:2px; }
 #Mouse{ position:absolute; display:none;color:blue;}
 #Mouse strong{ color:#f00;}

JavaScript

function mouseMove(event){
    var event = window.event || event;
     var x_div = document.getElementById("x_div"),
         y_div = document.getElementById("y_div");
   
     
     
     x_div.style.top = event.clientY + "px";
     y_div.style.left = event.clientX + "px";
 }
 
 document.onmousemove = mouseMove;