导航栏样式无法展示

报错信息；Failed to resolve component: el-menu-item
If this is a native custom element, make sure to exclude it from component resolution via compilerOptions.isCustomElement.

原因：创建Vue组件那一块代码写错，写成了如下：

<script>
        const App = {
            data() {
                return {

                }
            },
        }

        Vue.createApp(App).mount('#app')
    </script>

实际 应该改为：

    <script>
        const App = {
            data() {
                return {

                };
            },
        };
        const app = Vue.createApp(App);
        app.use(ElementPlus);
        app.mount("#app");
    </script>

改完保存后样式可以正常展示