css关于visibility设置 “collapse”值问题_html/css_WEB-ITnose

var btns = document.getElementsByTagName('button'),    rows = document.getElementsByTagName('tr');btns[0].addEventListener('click', function () {  rows[1].className = 'vc';}, false);btns[1].addEventListener('click', function () {  rows[1].className = 'vh';}, false);btns[2].addEventListener('click', function () {  rows[1].className = '';}, false);

body {  text-align: center;  padding-top: 20px;  font-family: Arial, sans-serif;}table {  border-collapse: separate;  border-spacing: 5px;  border: solid 1px black;  width: 500px;  margin: 0 auto;}th, td {  text-align: center;  border: solid 1px black;  padding: 10px;}.vc {  visibility: collapse;}.vh {  visibility: hidden;}button {  margin-top: 5px;}