multiplication table

function main(lines) {
    let n=Number(lines[0]);
    console.log("<table border='1'>");
    let firstRow="<tr><th>x</th>";
    for (let i = 1; i <= n; i++) {
        firstRow+="<th>"+i+"</th>";
    }
    firstRow+="</tr>";
    console.log(firstRow);

    for (let i = 1; i <= n; i++) {
        let nextRow="<tr><th>"+i+"</th>";
        for (let k = 1; k <= n; k++) {
            nextRow+="<td>"+i*k+"</td>";
        }
        nextRow+="</tr>";
        console.log(nextRow);
    }

    console.log("</table>");
}

// main(['5']);

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="test.js"></script>
</head>
<body>

<script>
    document.body.innerHTML=main(['5']);
</script>
</body>
</html>