<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<table border="1" width="300px">
<tr><td>1</td><td>2</td><td>3</td></tr>
<tr><td>1</td><td>2</td><td>3</td></tr>
<tr><td>1</td><td>2</td><td>3</td></tr>
</table>
<script>
var myTrs = document.getElementsByTagName('tr');
var len =myTrs.length;
for(var i=0;i<len;i++){
myTrs[i].onmouseover=function () {
// 谁调用的函数this就会指向谁
this.style.backgroundColor='red'
}
myTrs[i].onmouseout=function () {
// 谁调用的函数this就会指向谁
this.style.backgroundColor=''
}
}
</script>
</body>
</html>