JSFiddle - React, Tailwind, and code Playground

HTML

<canvas width="500" height="500" id="debug"></canvas>
<canvas width="502" height="502" id="content"></canvas>

CSS

#debug
{
    cursor:none;
    border: 1px solid #000000;
    position:absolute;
    z-index: 1;
}

JavaScript

var canvas = document.getElementById("debug");
var context = canvas.getContext("2d");
var c = document.getElementById("content");
var co = c.getContext("2d");
canvas.addEventListener("mousemove", function(event){        
 //   var contDiv = $('#current_system_map'); 
 //   var offset = contDiv.offset();
 /*   x = e.clientX-offset.left;
    y = e.clientY-offset.top; */
    var x = event.pageX - canvas.offsetLeft;
    var y = event.pageY - canvas.offsetTop;
    context.clearRect(0, 0, canvas.width, canvas.height);       
    context.beginPath();
    context.moveTo(0,y);
    context.lineTo(595,y);
    context.moveTo(x,0);
    context.lineTo(x,595);
    context.strokeStyle = "black";//"rgb(255,255,255)";
    context.stroke();   
    context.closePath();
    
});

co.beginPath();
co.moveTo(0,0);
co.lineTo(500,500);
co.strokeStyle = "red";
co.stroke();
co.closePath();