<span>
      <img :src="imgHtml" class="img">
</span>
<el-button type="primary" @click="toggleCode">换一张</el-button>

<script>
    export default {
        data() {
            return {
                imgHtml: 'url'
            }
        },
        methods: {
                        // 点击图片修改图片src
            toggleCode() {
                var num=Math.ceil(Math.random()*10);//生成一个随机数（防止缓存）
                this.imgHtml = "url?" + num;
            },
                }
        }
</script>