JSFiddle - React, Tailwind, and code Playground

HTML

<div id="parent">

</div>

CSS

.childDiv {
  width: 30px;
  height: 30px;
  margin-bottom: 5px;
}

JavaScript

let parentDiv = document.getElementById("parent");
for (let i = 0; i < Number(2); i++)
    {
        for (let j = 0; j < Number(5); j++)
        {                               
            let childDiv = document.createElement("div");
            childDiv.className = "childDiv";
            childDiv.style.backgroundColor = "#e6e6e6";
            childDiv.id = `${i};${j}`
            childDiv.onclick = () => childDiv.style.backgroundColor = "black";
            childDiv.onmouseenter = () => childDiv.style.background = "#cccccc";                
            childDiv.onmouseleave = () => childDiv.style.background = "#e6e6e6";
            parentDiv.appendChild(childDiv); 
        }           
    }