JSFiddle - React, Tailwind, and code Playground

HTML

<head>
    <script>
        $(window).load(function() {
            var tooltip = $('<div id="tooltip">').appendTo('body')[0];

            $('.coords').
            each(function() {

                var pos = $(this).offset(),
                    top = pos.top,
                    left = pos.left,
                    width = $(this).width(),
                    height = $(this).height();

                $(this).
                mousemove(function(e) {
                    var x = ((e.clientX + document.body.scrollLeft + document.documentElement.scrollLeft) - left).toFixed(0),
                        y = (((e.clientY + document.body.scrollTop + document.documentElement.scrollTop) - top)).toFixed(0);


                        $(tooltip).text( x + ', ' + y ).css({
                            left: e.clientX + 20,
                            top: e.clientY + 10
                        }).show();


                }).

                mouseleave(function() {
                    $(tooltip).hide();
                });

            });

        });
    </script>

</head>

CSS

.grid {
        margin: 0px auto auto;
        border: 1px solid #000;
        border-width: 0 1px 1px 0;
        background-color: #CCC;
      }

      .grid div {
        border: 1px solid #000;
        border-width: 1px 0 0 1px;
        float: left;
}
      #tooltip { 
        text-align:center; 
        background:black; 
        color:white; 
        padding:3px 0; 
        width:150px; 
        position:fixed; 
        display:none; 
        white-space:nowrap;
        z-index:3; 
      }

JavaScript

function creategrid(size){
  
              var standardW = Math.floor((500) / size),
                  standardH = Math.floor((500) / size);

              var standard = document.createElement('div');
                  standard.className = 'grid coords';
                  standard.style.width = (standardW * size) + 'px';
                  standard.style.height = (standardH * size) + 'px';

                for (var i = 0; i < standardH; i++) {
                    for (var p = 0; p < standardW; p++) {
                      var cell = document.createElement('div');
                          cell.style.height = (size - 1) + 'px';
                          cell.style.width = (size - 1) + 'px';
                          cell.style.position = 'relative'
                          cell.style.zIndex= '2';
                standard.appendChild(cell);
                    }
                }

              document.body.appendChild(standard);
          }

          creategrid(10);