<table>
  <tbody></tbody>
</table>

table, td {
  border: 1px solid #CCC;
  border-collapse: collapse;
}
td {
  padding: 5px;
  text-align: center;
  font-family: Helvetica, Tahoma, sans-serif;
  color: #333;
}

const length = 10;
const tbody = document.querySelector('table > tbody');

Array.from({length}, () => {
  const tr = document.createElement('tr');
  tr.classList.add('line');
  Array.from({length}, () => {
    const n = 1 + Math.random() * 100 | 0;
    const td = document.createElement('td');
    td.classList.add('box');
    td.innerText = n;
    tr.appendChild(td);
  });
  tbody.appendChild(tr);
});