解决vue2.0 element-ui中el-upload的before-upload方法返回false时submit()不生效问题

<el-upload
   class="upload-demo" drag
   ref="fileUpload"
   :action="urls.fileUpload"
   :on-success="handleUploadSuccess"
   :on-error="handleUploadError"
   :on-progress="progressUpload"
   :before-upload="beforeUpload"
   show-file-list
   multiple>
   <i class="el-icon-upload"></i>
  <div class="el-upload__text">点击上传，或者拖拽到这里</div>
 </el-upload>

<template>
 <div class="uptemp">
  <el-upload
   class="upload-demo"
   ref="upload"
   multiple="false"
   action="/web/api/uploadFile"
   :on-preview="handlePreview"
   :on-remove="handleRemove"
   :on-change="handleChange"
   :before-upload="beforeUpload"
   :file-list="fileList"
   :auto-upload="false"
   :multiple="false">
   <el-button slot="trigger" size="small" type="primary">选取文件</el-button>
   <el-button style="margin-left: 10px;" size="small" type="success" @click="submitUpload">导入</el-button>
   <div slot="tip" class="el-upload__tip">只能上传jpg/png文件</div>
  </el-upload>
 </div>
</template>
<script>
 export default {
  data() {
   return {
    fileList: []
   }
  },
  mounted: function () {
   //加载完页面执行的函数
  },
  methods: {
   submitUpload() {
    this.$refs.upload.submit();
   },
   handleRemove(file, fileList) {
    console.log(file, fileList);
   },
   handlePreview(file) {
    console.log(file);
   },
   handleChange(file, fileList){
    console.log(file);
    console.log(fileList);
   },
   beforeUpload: function (file) {
    console.log(file)
    //这里是重点，将文件转化为formdata数据上传
    let fd = new FormData()
    fd.append('file', file)
    this.$http.post('/web/api/uploadFile', fd).then((res) => {
     console.log(res)
    }, (res) => {
     console.log(res)
    });
    return false;
   }
  },
  components: {
//      组件
  }
 }
</script>
<style scoped>
</style>
<style>
 .uptemp .el-upload-list {
  position: absolute;
  left: 140px;
  top: 0;
  width: 50%;
 }
 .uptemp {
  position: relative;
 }
 .uptemp .el-upload-list .el-upload-list__item {
  margin-top: 0;
 }
</style>