js方法

<script src="http://unpkg.com/element-ui@1.4.1/lib/index.js"></script>
<div id="app" ref = 'find'>
<el-upload action="https://jsonplaceholder.typicode.com/posts/" list-type="picture-card" :on-preview="handlePictureCardPreview" :on-remove="handleRemove" :on-change = "handleChange">
  <i class="el-icon-plus"></i>
</el-upload>
<el-dialog v-model="dialogVisible" size="tiny">
  ![](dialogImageUrl)
</el-dialog>
</div>

var Main = {
    data() {
      return {
        dialogImageUrl: '',
        dialogVisible: false
      };
    },
    methods: {
     handleChange () {
     this.$refs.find.querySelector(".el-upload--picture-card").style.background = 'red'
     },
      handleRemove(file, fileList) {
      this.$refs.find.querySelector(".el-upload--picture-card").style.background = 'green'
        console.log(file, fileList);
      },
      handlePictureCardPreview(file) {
        this.dialogImageUrl = file.url;
        this.dialogVisible = true;
      }
    }
  }
var Ctor = Vue.extend(Main)
new Ctor().$mount('#app')

image.png

另一種思維：
也可以在外層包個(gè)class,然后設(shè)置class寬度
超出部分隱藏overflow:hidden

image.png

image.png

這里其實(shí)應(yīng)給el -form-item單獨(dú)設(shè)立class也可實(shí)現(xiàn)這個(gè)效果
:on-change 可以改為 ：on-sucess 當(dāng)上傳成功后再進(jìn)行操作