jquery-$(this).find()不是函数

modal component

<div class="modal fade" id="formMail" tabindex="-1" rmle="dialog" aria-labelledby="formMailLabel" aria-hidden="true">
    <div class="modal-dialog modal-dialog-centered" role="document">
        <div class="modal-content">
            <div class="modal-header">
                <h5 class="modal-title" id="formMail_title">Send</h5>
                <button type="button" class="close" data-dismiss="modal" aria-label="Close">
                    <span aria-hidden="true">&times;</span>
                </button>
            </div>
            <div class="modal-body">
            </div>
            <div class="modal-footer">
            </div>
        </div>
    </div>
</div>

<script type="text/javascript">

    $('#formMail').on('show.bs.modal', function (event) {
        var modal = $(this);
        modal.find('.modal-title').text('It works!'); // <<<< problem here!
    })

</script>

我对find函数有问题。我不是jquery方面的专家,但当我使用$(this)时,我认为它将被视为jquery对象。

Uncaught TypeError: modal.find is not a function
    at HTMLDivElement.<anonymous> (cursos:439)
    at HTMLDivElement.dispatch (jquery-3.3.1.min.js?ver=3.3.1:2)
    at HTMLDivElement.y.handle (jquery-3.3.1.min.js?ver=3.3.1:2)
    at Object.trigger (jquery-3.3.1.min.js?ver=3.3.1:2)
    at HTMLDivElement.<anonymous> (jquery-3.3.1.min.js?ver=3.3.1:2)
    at Function.each (jquery-3.3.1.min.js?ver=3.3.1:2)
    at w.fn.init.each (jquery-3.3.1.min.js?ver=3.3.1:2)
    at w.fn.init.trigger (jquery-3.3.1.min.js?ver=3.3.1:2)
    at o.p.show (modal.js:121)
    at HTMLDivElement.<anonymous> (modal.js:516)

我错过什么了吗?