1var whiteList = ["rowspan", "colspan"];
 2
 3[...document.querySelectorAll("table")].forEach(table => {
 4  rmAttr(table);
 5  [...table.querySelectorAll("tr")].forEach(tr => {
 6    rmAttr(tr);
 7    [...tr.querySelectorAll("td")].forEach(td => {
 8      rmAttr(td);
 9    });
10  });
11  console.log(table.outerHTML);
12});
13
14function rmAttr(dom) {
15  [...dom.attributes].forEach(attr => {
16    if (!~whiteList.indexOf(attr.name)) {
17      dom.removeAttribute(attr.name);
18    }
19  });
20}