参考：https://www.jianshu.com/p/07c27e576b26

    css，把input隐藏，美化label即可。

    1. .inputfile {
    2.     width: 0.1px; 
    3.     height: 0.1px; 
    4.     opacity: 0; 
    5.     overflow: hidden; 
    6.     position: absolute; 
    7.     z-index: -1;
    8. }

    html

    1. <input type='file' id='file' class='inputfile' webkitdirectory >  
    2. <label for="file">Choose a file</label>

    js

    1. var files = [];
    2. $(document).ready(function(){
    3.   $("#file").change(function(){
    4.     files = this.files;
    5.   });
    6. });
    7. $("#upload-btn").click(function(){
    8.   var fd = new FormData();
    9.   for (var i = 0; i < files.length; i++) {
    10.     fd.append("files", files[i]);
    11.   }
    12. });
    14. axios.post("url",data,{
    15.     headers:{
    16.         "Content-Type": "multipart/form-data",
    17.     }
    18. });