<head>
<meta charset="utf-8">
<title></title>
<script type="text/JavaScript">
function sum(x,y,z)
{
sum = x + y +z;
document.write(x+"、"+y+"、"+z+"和:"+sum+"<br/>");
}
sum(5,8,3);
sum(7,1,4);
</script>
</head>
<body>
</body>
这两个调用sun的函数为什么只执行了前一个