您需要单击一个按钮来添加新列和新行，代码可以工作，但不完全。再次单击按钮时，行末尾的单元格不会添加，并且表格像梯子一样移动，我不明白缺少什么。
let table = document.getElementById('table');
let button = document.getElementById('button');
for (let i = 1; i <= 2; i++) {
let tr = document.createElement('tr');
for (let j = 1; j <= 2; j++) {
let td = document.createElement('td');
td.textContent = j;
tr.append(td)
}
table.append(tr)
}
button.addEventListener('click', function() {
let tr = document.createElement('tr');
for (let i = 1; i <= 2; i++) {
let td = document.createElement('td');
td.textContent = i;
tr.append(td);
}
table.append(tr)
let trs = document.querySelectorAll('#table tr');
for (let tr of trs) {
let td = document.createElement('td');
td.textContent = 'new';
tr.appendChild(td);
}
})<table id="table"></table>
<button id="button">click me</button>