<form id="uploadform" method="POST" enctype="multipart/form-data" :action="postImgApi" ref="uploadform">
 <input type="file" name="imagefile" @change="upload" ref="inputfile">
</form>
let uploadform = this.$refs.uploadform
let inputfile = this.$refs.inputfile
let formData = new FormData(uploadform) //初始化时将form Dom对象传入
formData.append('imagefile', inputfile) //将imagefile键追加进去，值为input-file的dom对象，否则服务端无法获取file
this.$http.post(this.postImgApi, formData, {
 headers: {
  'Content-Type': 'multipart/form-data' //设置post文件的请求头
 }
}).then(res => {
 debugger
 this.textarea = res.data
})