你可能想要保持jquery.js延迟，以更快的页面加载。但是，如果jquery.js被延迟到$(window)。负载可能不工作。那么你可以试试

setTimeout（function（）{$（'#myModal'）.modal（'show'）;}，3000）;

它会在页面完全加载后弹出你的模态(包括jquery)

更新2020 -引导5

建立在优秀的回应从以前的答案，在Bootstrap 5没有jQuery，这已经工作;

document.querySelector('[data-target="#exampleModal"]').click();

完整的片段:

window.onload = () => { document.querySelector('[data-target="#exampleModal"]').click(); } <script src="https://stackpath.bootstrapcdn.com/bootstrap/5.0.0-alpha1/js/bootstrap.min.js"></script> <script src="https://cdn.jsdelivr.net/npm/popper.js@1.16.0/dist/umd/popper.min.js"></script> <link href="https://stackpath.bootstrapcdn.com/bootstrap/5.0.0-alpha1/css/bootstrap.min.css" rel="stylesheet" /> <div class="container py-3"> <!-- Button trigger modal --> <button type="button" class="btn btn-primary" data-toggle="modal" data-target="#exampleModal"> Launch demo modal </button> <!-- Modal --> <div class="modal fade" id="exampleModal" tabindex="-1" aria-labelledby="exampleModalLabel" aria-hidden="true"> <div class="modal-dialog"> <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>

使用Bootstrap 3和jQuery(2.2和2.3)进行测试

$(window).on('load',function(){
  $('#myModal').modal('show');
});



<!-- Modal -->
<div class="modal fade" id="myModal" role="dialog">
    <div class="modal-dialog">

      <!-- Modal content-->
      <div class="modal-content">
        <div class="modal-header">
          <button type="button" class="close" data-dismiss="modal">&times;</button>
          <h4 class="modal-title"><i class="fa fa-exclamation-circle"></i>&nbsp; //Your modal Title</h4>
        </div>
        <div class="modal-body">
          //Your modal Content
        </div>
        <div class="modal-footer">
          <button type="button" class="btn btn-default" data-dismiss="modal">Fechar</button>
        </div>
      </div>

    </div>
</div>

https://jsfiddle.net/d7utnsbm/

<div id="ModalStart" class="modal" tabindex="-1" role="dialog" aria-labelledby="myModalLabel" aria-hidden="true">
    <div class="modal-body">
          <p><i class="icon-spinner icon-spin icon-4x"></i></p>
    </div>
</div>

即使没有Javascript，你也可以在开始时显示它。只需删除类“hide”。

class="Modal"

除了user2545728和Reft的答案，没有javascript，但与情态背景

添加3件事

一个在.modal类之前带有modal- background类的div Style ="display:block;"到.modal类 与.modal类一起淡出

例子

<div class="modal-backdrop in"></div>

<div class="modal fade in" tabindex="-1" role="dialog" aria-labelledby="channelModal" style="display:block;">

    <div class="modal-dialog modal-lg" role="document">

        <div class="modal-content">

            <div class="modal-header">

                <h4 class="modal-title" id="channelModal">Welcome!</h4>

            </div>

            <div class="modal-body" style="height:350px;">

                How did you find us?

            </div>

        </div>

    </div>

</div>

您可以尝试这个可运行的代码-

$(window).load(function() { $('#myModal').modal('show'); }); <link rel="stylesheet" href="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css"> <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.0/jquery.min.js"></script> <script src="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js"></script> <div class="container"> <!-- Trigger the modal with a button --> <button type="button" class="btn btn-info btn-lg" data-toggle="modal" data-target="#myModal">Open Modal</button> <!-- Modal --> <div class="modal fade" id="myModal" role="dialog"> <div class="modal-dialog"> <!-- Modal content--> <div class="modal-content"> <div class="modal-header"> <button type="button" class="close" data-dismiss="modal">&times;</button> <h4 class="modal-title">Modal Header</h4> </div> <div class="modal-body"> <p>Some text in the modal.</p> </div> <div class="modal-footer"> <button type="button" class="btn btn-default" data-dismiss="modal">Close</button> </div> </div> </div> </div> </div>

更多信息可以在这里找到。

我想你已经有了完整的答案。