6.9 检验 Zip 编码

简单校验纯数字
<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <script>
        function isNum(number) {
            if (number == "") {
                return false;
            }
            for (var k=0; k<number.length;k++) {
                if (number.charAt(k) < "0") {
                    return false;
                }
                if (number.charAt(k) > "9") {
                    return false; }
            }
            return true;
        }
        function check() {
            var x = document.getElementById("code").value;
            if (isNum(x)) {
                return true;
            } else  {
                alert("必须纯数字");
                return false;
            }
        }
    </script>
</head>
<body>
<form name="myForm" action="demo_form.php" onsubmit="return check()" method="post">
    <label><input type="text" id="code" name="code"></label>
    <input type="submit" value="提交">
</form>
</body>
</html>