从上一个TR删除样式

var table = document.getElementById("myTable");
var row = table.insertRow(0);
var cell1 = row.insertCell(0);
var cell2 = row.insertCell(1);
cell1.innerHTML = "NEW CELL1";
cell2.innerHTML = "NEW CELL2";

table {
  border-collapse: collapse;
  width: 100%;
}

th, td {
  text-align: left;
  padding: 8px;
}

tr:nth-child(even){background-color: #f2f2f2}

th {
  background-color: #4CAF50;
  color: white;
}