<!DOCTYPE html>
<html>
<head>
    <style>
        body{
            background: #a3cfe0;
        }
        .blackcell{
            display: inline-block;
            width: 50px;
            height: 50px;
            background: black;
        }
        .whitecell{
            display: inline-block;
            width: 50px;
            height: 50px;
            background: white;
        }
    </style>
</head>
<body>
    <div id="board"></div>

    <script>
        function board(size){
            let result = "";
            for(let i = 0; i < size; i++){
                result += "<div>\n";
                for(let j = 0; j < size; j++){
                    let cls = ((i+j)%2 == 0) ? "blackcell" : "whitecell";
                    result += "<div class=\"" + cls + "\"></div>\n";
                }
                result += "</div>\n";
            }
            return result;
        }

        document.getElementById("board").innerHTML = board(8);
    </script>
</body>
</html>