JSFiddle - React, Tailwind, and code Playground

HTML

<div class="main"></div>

JavaScript

function init(){
//board init
var width = parseInt(prompt ("Width?", "10"));
var height = parseInt(prompt ("Height?", "10"));
var board = [];

for (var i = 0; i <= height; i++){
  board[i] = [];
  for (var k = 0; k <= width; k++){
    board[i][k]={};
  }
}

//init html board
for (var a = 0; a < board.length; a++){
  //create parent div + pick him style
  var divRow = document.createElement("div");
  divRow.className = "row";
  var parentElementRow = document.querySelector(".main");
  parentElementRow.appendChild(divRow);
  for (var c = 0; c < board[a].length; c++){
    // create child div + pick him style
    var divCol = document.createElement("div");
    divCol.className = "col";
    var parentElementCol = document.querySelector(".main").lastChild;
    parentElementCol.appendChild(divCol);
    }
  }
}
init();