Vue.js 原生 FormData 实现无刷新图片上传

<template>
 <div class="admin">
 <div class="admin-content">
  <div class="edit">
  <div class="avatar">
   <div class="img">
   <img :src="avatar" @click="setAvatar">
   <span>更改</span>
   </div>
   <input type="file" name="avatar" accept="image/gif,image/jpeg,image/jpg,image/png" style="display:none" @change="changeImage($event)" ref="avatarInput">
  </div>
  <button type="button" @click="edit">确认修改</button>
  </div>
 </div>
 </div>
</template>
<script>
export default {
 data() {
 return {
  avatar: this.$store.state.administrator.avatar,
 }
 },
 methods: {
 edit() {
  // 修改了头像
  if (this.$refs.avatarInput.files.length !== 0) {
   var image = new FormData()
   image.append('avatar', this.$refs.avatarInput.files[0])
   this.axios.post('/avatar', image, {
   headers: {
    "Content-Type": "multipart/form-data"
   }
   })
  }
  }) 
 },
 setAvatar() {
  this.$refs.avatarInput.click()
 },
 changeImage(e) {
  var file = e.target.files[0]
  var reader = new FileReader()
  var that = this
  reader.readAsDataURL(file)
  reader.onload = function(e) {
  that.avatar = this.result
  }
 }
 }
}
</script>

exports.avatar = function(req, res, next) {
 let form = new formidable.IncomingForm()
 form.parse(req, function(err, fields, files) {
 if (err) {
  return res.json({
  "code": 500,
  "message": "内部服务器错误"
  })
 }

 // 获取后缀名
 let extname = path.extname(files.avatar.name)
 let oldpath = files.avatar.path;
 let newpath = './public/avatar' + extname;
 let avatarName = 'avatar' + extname;
 // 更改名字和路径
 fs.rename(oldpath, newpath, function(err) {
  if (err) {
  return res.json({
   "code": 401,
   "message": "图片上传失败"
  })
  }
 })
 // 更新数据库
 db.updateMany('users', { "user": username }, { "avatar": avatarName },
  function(err, result) {
  if (err) {
   return res.json({
   "code": 401,
   "message": "头像更新失败"
   })
  }
  return res.json({
   "code":200,
   "message": "头像上传成功"
  })
  })
 })
}