SOURCE

const { createApp, onMounted, onBeforeMount } = Vue;
const app = createApp({
    data(){
        return {
            aa: 1
        }
    },
    setup() {
        console.log(11111);
        onBeforeMount(() => {
            console.log('onBeforeMount')
        });
        onMounted(() => {
            console.log('onMounted')
        });
    }
}).mount("#app")

<div id="app">{{aa}}</div>