简单实现js上传文件功能

<form id="upload" enctype="multipart/form-data" method="post"> 
 <input type="file" name="file" id="pic"/> 
 <input type="button" value="提交" onclick="uploadPic();"/> 
 <span class="showUrl"></span> 
 <img src="" class="showPic" alt=""> 
</form> 

function uploadPic() { 
  var form = document.getElementById('upload'), 
    formData = new FormData(form); 
  $.ajax({ 
   url:"https://sscpre.boe.com/v1/medical-console/medical/file/upload", 
   type:"post", 
   data:formData, 
   processData:false, 
   contentType:false, 
   success:function(res){ 
    if(res){ 
     alert("上传成功！"); 
    } 
    console.log(res); 
    $("#pic").val(""); 
    $(".showUrl").html(res); 
    $(".showPic").attr("src",res); 
   }, 
   error:function(err){ 
    alert("网络连接失败,稍后重试",err); 
   } 
 
  }) 
 
 }