Twitter bootstrap modal listen when scrollbar at bottom

Question

I'm using Twitter bootstrap modal and I don't know how listen when the scrollbar of the modal reach the bottom of the modal in Javascript or with jQuery.

I'm listening the scroll event for the modal like that :

$('.modal-body').scroll(function() {
    //do something when scrollbar reach the modal's bottom      
});

Thank's for help.

Answer 1

Adding .scrollTop() to .innerHeight() you get where should be the modal body. Compare this value with scrollHeight and that's all:

$('#exampleModalLong .modal-body').on('scroll', function() {
    if($(this).scrollTop() + $(this).innerHeight() >= $(this)[0].scrollHeight) {
        console.log('end reached');
    }
})

.modal-body{
    height: 250px;
    overflow-y: auto;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.0/css/bootstrap.min.css">
<script src="https://cdn.jsdelivr.net/npm/popper.js@1.16.0/dist/umd/popper.min.js"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.5.0/js/bootstrap.min.js"></script>


<!-- Button trigger modal -->
<button type="button" class="btn btn-primary" data-toggle="modal" data-target="#exampleModalLong">
    Launch demo modal
</button>

<!-- Modal -->
<div class="modal fade" id="exampleModalLong" tabindex="-1" role="dialog" aria-labelledby="exampleModalLongTitle" aria-hidden="true">
    <div class="modal-dialog" role="document">
        <div class="modal-content">
            <div class="modal-header">
                <h5 class="modal-title" id="exampleModalLongTitle">Modal title</h5>
                <button type="button" class="close" data-dismiss="modal" aria-label="Close">
                    <span aria-hidden="true">&times;</span>
                </button>
            </div>
            <div class="modal-body">
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
                <p>..............</p>
            </div>
            <div class="modal-footer">
                <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button>
                <button type="button" class="btn btn-primary">Save changes</button>
            </div>
        </div>
    </div>
</div>