详解vue 图片上传功能

<ul class="clearfix">
        <li v-if="imgs.length>0" v-for='(item ,index ) in imgs'>
          <img :src="item">
        </li>
        <li style="position:relative" v-if="imgs.length>=6 ? false : true">
          <img src="../../assets/img/addimg.png"><input class="upload" @change='add_img' type="file">
        </li>
</ul>

data () {
  return {
    imgs: [],
    imgData: {
      accept: 'image/gif, image/jpeg, image/png, image/jpg',
    }
  }
 }

add_img(event){ 
      let reader =new FileReader();
      let img1=event.target.files[0];
      let type=img1.type;//文件的类型，判断是否是图片
      let size=img1.size;//文件的大小，判断图片的大小
      if(this.imgData.accept.indexOf(type) == -1){
        alert('请选择我们支持的图片格式！');
        return false;
      }
      if(size>3145728){
        alert('请选择3M以内的图片！');
        return false;
      }
      var uri = ''
      let form = new FormData(); 
      form.append('file',img1,img1.name);
      this.$http.post('/file/upload',form,{
        headers:{'Content-Type':'multipart/form-data'}
      }).then(response => {
        console.log(response.data)
        uri = response.data.url
        reader.readAsDataURL(img1);
        var that=this;
        reader.onloadend=function(){
          that.imgs.push(uri);
        }
      }).catch(error => {
        alert('上传图片出错！');
      })  
},