vue element el-upload 接收不到響應(yīng)結(jié)果

<el-upload class="upload-demo" ref="upload" 
      drag
      :action="actions"
      :headers="setHeaders"
      :on-preview="handlePreview"
      :on-remove="handleRemove"
      :file-list="fileList"
      :on-error="uploadFail"
      :on-success="uploadSuccess"
      :auto-upload="false"
      :multiple="false">
      <el-button slot="trigger" size="small" type="primary">選取文件</el-button>
      <el-button style="margin-left: 10px;" size="small" type="success" @click="submitUpload">上傳到服務(wù)器</el-button>
      <div slot="tip" class="el-upload__tip">只能上傳jpg/png文件，且不超過500kb</div>
      </el-upload>
      
      
      
      methods: {
      submitUpload() {
        this.$refs.upload.submit();
      },
      handleRemove(file, fileList) {
        console.log(file, fileList);
      },
      handlePreview(file) {
        console.log(file);
      },
      uploadSuccess(res,file,fileList){
            console.log(res);
            console.log(file);
            console.log(fileList);
     },
     uploadFail(res,file,fileList){
            console.log(res);
            console.log(file);
            console.log(fileList);
     }
      
  }

uploadSuccess得到的結(jié)果是空的，不知道什么原因

實(shí)際瀏覽器是有的