js隐藏和显示表格

<style>
body{font-size:30px;}
tr{display:none}
input{width:400px;height:50px;font-size:30px;}
</style>

<script>
window.onload = function init() {
var trs = document.getElementsByTagName("tr");

for (var i = 0; i < trs.length; i++) {
trs[i].style.display="table-row";
}
alert("trs = " + trs.length);

}
</script>