Untitled

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>Валидация номера</title>
    <script type="text/javascript">
    function checkNumber() {
        var re_numb = new RegExp("/\b89\d\d\d\d\d\d\d\d\d\\b/", 'g');
        var phone_numb = document.getElementById("number").value;
        // var valid = re_numb.test(phone_numb);
        alert(phone_numb);
        if (re_numb.test((phone_numb.toString()))) {
            alert("It's correct");
        } else {
            alert("Panic");
        }
    }
    </script>
</head>
<body>
    <input type="text" name="number" id="number">
    <input type="image" src="images/button.png" alt="go" style="width:18px;height:18px" onclick="checkNumber()">
</body>
</html>