Centered modal load spinner bootstrap 4

Question

I want a modal load spinner and have based a test on Bootstrap 4's modal dialog box. However, I can't get the modal horizontally centered on the page. If possible, I would also like the modal to be with no borders and transparent (so it appears that only the spinner is hovering over the page)

Answer 1

Apply this two classes:

.bd-example-modal-lg .modal-dialog{
    display: table;
    position: relative;
    margin: 0 auto;
    top: calc(50% - 24px);
  }

  .bd-example-modal-lg .modal-dialog .modal-content{
    background-color: transparent;
    border: none;
  }

function modal(){
       $('.modal').modal('show');
       setTimeout(function () {
       	console.log('hejsan');
       	$('.modal').modal('hide');
       }, 3000);
    }

.bd-example-modal-lg .modal-dialog{
    display: table;
    position: relative;
    margin: 0 auto;
    top: calc(50% - 24px);
  }
  
  .bd-example-modal-lg .modal-dialog .modal-content{
    background-color: transparent;
    border: none;
  }

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta.3/css/bootstrap.min.css" integrity="sha384-Zug+QiDoJOrZ5t4lssLdxGhVrurbmBWopoEl+M6BdEfwnCJZtKxi1KgxUyJq13dy" crossorigin="anonymous">
  <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css">
  <script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
  <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta.3/js/bootstrap.min.js" integrity="sha384-a5N7Y/aK3qNeh15eJKGWxsqtnX/wWdSZSKp+81YjTmS15nvnvxKHuzaWwXHDli+4" crossorigin="anonymous"></script>

  
<button type="button" class="btn btn-primary" onclick="modal();">Open and close in 3 secs</button>

<div class="modal fade bd-example-modal-lg" data-backdrop="static" data-keyboard="false" tabindex="-1">
    <div class="modal-dialog modal-sm">
        <div class="modal-content" style="width: 48px">
            <span class="fa fa-spinner fa-spin fa-3x"></span>
        </div>
    </div>
</div>
<p>I would like the <ul><li>spinner horizontally centered on page<li> the modal transparent without borders</ul></p>