let arr = [ 1, 2, 3, 4, 5, 6, 7] ;
for (let i = 0; i <= arr.length; i++) {
document.write(i);
}
const arr = [ 1, 2, 3, 4, 5, 6, 7] ;
const html = `<table><tbody>
${ arr.map(n => `<tr><td>${n}</td></tr>`).join() }
</tbody></table>`;
document.write(html); // вообще так лучше не делать
const table = document.createElement('table');
const rows = arr.map(n => `<tr><td>${n}</td></tr>`).join();
table.innerHTML = rows;
document.body.appendChild(table);