JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://lunarlogic.github.io/dolly.js/javascripts/dolly.js"></script>
<body></body>

CSS

td {
    border: 3px solid #ccc;
    margin: 0;
    width: 20px;
    height: 20px;
    padding: 10px;
}
table {
    border-collapse: none;
    border-spacing: 0;
    border: 3px solid #ccc;
}

JavaScript

var tableController = {
    onClone: function (el, cloneX, cloneY, indexX, indexY) {
        var row = $(el).closest('tr'),
            dirX = cloneX > 0 ? 1 : -1,
            dirY = cloneY > 0 ? 1 : -1,
            amountX = Math.abs(cloneX),
            amountY = Math.abs(cloneY);
        for (var i = indexY; amountY >= 0; i += dirY, amountY--) {
            var amX = amountX;
            for (var j = indexX; amX >= 0; j += dirX, amX--) {
                this.data[i][j] = this.data[indexY][indexX];
            }
        }
        this.render();
    },

    render: function () {
        var self = this;
        this.element.html("");
        for (var i = 0, len = this.data.length; i < len; i++) {
            var row = $("<tr></tr>");
            for (var j = 0, lenj = this.data[i].length; j < lenj; j++) {
                var cell = $("<td></td");
                cell.html(this.data[i][j]);
                row.append(cell);
            }
            this.element.append(row);
        }
        $("td").dolly({
        		allowDiagonalSelection: true,
            cloned: function (event, ui) {
                self.onClone(this, ui.cloneX, ui.cloneY, ui.originX, ui.originY);
            },
            boxStyle: {
                "background-color": "rgba(255, 0, 0, 0.2)",
                border: "3px red dotted"
            },
            handleStyle: {
                width: "0",
                height: "0",
                "background-color": "transparent",
                "border-top": "7px solid transparent",
                "border-bottom": "7px solid black",
                "border-right": "7px solid black",
                "border-left": "7px solid transparent"
            }
        });
    }
};

tableController.element = $("<table></table>").appendTo("body");
tableController.data = [];
for (var i = 0; i < 5; i++) {
    tableController.data.push([]);
    for (var j = 0; j < 5; j++) {
        tableController.data[i].push(Math.floor(Math.random() * 100));
   ...