问在SharePoint 2013页面中加载gif

EN

<img src="/_layouts/15/images/loading16.GIF" style="display: none;" id="img">
<input type="button" value="download" id="download">
<script src="https://cdn.bootcdn.net/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
<script src="https://cdn.jsdelivr.net/gh/gitbrent/sprestlib@1.8.0/dist/sprestlib.min.js"></script>
<script>
  $("#download").click(function(){
    $("#img").css("display","");
    sprLib.file('Doc/Presentation.pptx').get()
      .then(function (blob) {
        var url = (window.URL || window.webkitURL).createObjectURL(blob);
        var link = document.createElement("a");
        link.setAttribute("href", url);
        link.setAttribute("download", _fileName);
        link.style = "visibility:hidden";
        document.body.appendChild(link);
        link.click();
        setTimeout(function () { document.body.removeChild(link); }, 500);
      }).then(function(){
        $("#img").css("display","none");
      });
  })    
</script>