文件上传 ：form-data格式

//HTML

      <div class="beacone_right-btn autoM" onclick="uploadPic();">立即缴纳</div>
      <input type="file" name="file" id="pic" />

//formData上传文件
    function uploadPic() {
        var formData = new FormData()
        formData.append("file", $('#pic')[0].files[0])
        console.log($('#pic')[0].files)
        console.log(formData)
        $.ajax({
            url: "/member/upload",
            type: "post",
            data: formData,
            processData: false,
            contentType: false,
            success: function (res) {
                console.log(res)
            }
        })
    }