<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>String对象</title>
<script>
var str = "-a-b-c-d-e-f-";
var str1 = str.substr(2,4);//-b-c
//alert(str1);
var str2 = str.substring(2,4);//-b
alert(str2);
</script>
</head>
<body>
</body>
</html>