JavaScript substr() 方法详解：语法、参数与示例

语法结构

string.substr(start[, length]);

<html>
<head>
<title>JavaScript String substr() Method</title>
</head>
<body>
<script type="text/javascript">

var str = "Apples are round, and apples are juicy.";

document.write("(1,2): "  + str.substr(1,2));
document.write("<br />(-2,2): "  + str.substr(-2,2));
document.write("<br />(1): "   + str.substr(1));
document.write("<br />(-20, 2): " + str.substr(-20,2));
document.write("<br />(20, 2): " + str.substr(20,2));

</script>
</body>
</html>

(1,2): pp
(-2,2): Ap
(1): pples are round, and apples are juicy.
(-20, 2): Ap
(20, 2): d