请问这个排序的算法，是怎么实现的？sortNum函数的有参函数为什么被无参调用了？
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Array对象 </title>
<script type="text/javascript">
function sortNum(a,b) {
return b - a;
}
var myarr = new Array("80","16","50","6","100","1");
document.write(myarr+"<br />");
document.write(myarr.sort(sortNum));
</script>
</head>
<body>
</body>
</html>
