<!--data-target 使用 ID-->
<div class="container my-3">
    <!-- Button trigger modal -->
    <button type="button" class="btn btn-primary" data-toggle="modal" data-target="#exampleModal">
        Large modal
    </button>

    <!-- Modal -->
    <div class="modal fade" id="exampleModal" tabindex="-1" role="dialog" aria-labelledby="exampleModalLabel"
        aria-hidden="true">
        <div class="modal-dialog modal-lg" role="document">
            <div class="modal-content">
                <div class="modal-header">
                    <h5 class="modal-title" id="exampleModalLabel">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">
                    ...
                </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>
</div>

<hr>
<!--data-target 使用 Class-->
<div class="container my-3">
    <!-- Button trigger modal -->
    <button type="button" class="btn btn-warning" data-toggle="modal" data-target=".bg-example-modal-sm">
        Small modal
    </button>

    <!-- Modal -->
    <div class="modal fade bg-example-modal-sm" tabindex="-1" role="dialog" aria-labelledby="exampleModalLabel"
        aria-hidden="true">
        <div class="modal-dialog modal-sm" role="document">
            <div class="modal-content">
                <div class="modal-header">
                    <h5 class="modal-title" id="exampleModalLabel">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">
                    ...
                </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>
</div>