Phone number regular expression

Format phone number for normal and toll free number

HTML

<div style="background:#ddd; position:relative; width:90%; padding:20px;">
    <p>Regular expression</p>
    <!-- INPUT -->
    <input id="assure_telephone" placeholder="Phone number" name="assure_telephone" maxlength="25" type="text" />
    <p><b>Expected results</b>
        <br/>111-222-3333
        <br/>111-222-3333 #44444</p>
    <hr/>
    <p><b>Problems</b></p>
    <ol>
        <li>If the number is not long enough, it might not work</li>
        <li>If we get a number without Ext. the # will still display</li>
        <li>If we type a toll-free number, it won't display correctly</li>
</div>

JavaScript

$('#assure_telephone').bind('change', function(){
    // Delete all caracters and specials caraters except numbers
    telephone_user = $('#assure_telephone').val().replace(/[^0-9]/g, '');

    // Format the new phone number
    telephone_user_regex = telephone_user.replace(/(\d{3})(\d{3})(\d{4})(\d{0,5})/, "$1-$2-$3 #$4");

    $('#assure_telephone').val(telephone_user_regex);
});