Get your own Vue server
  <h1>The 'beforeUpdate' Lifecycle Hook</h1>
  <p>Whenever there is a change in our page, the application is 'updated' and the 'beforeUpdate' hook happens just before that.</p>
  <p>It is safe to modify our page in the 'beforeUpdate' hook like we do here, but if we modify our page in the 'updated' hook, we will generate an infinite loop.</p>
  <button @click="this.activeComp = !this.activeComp">Add/Remove Component</button>
    <comp-one v-if="activeComp"></comp-one>
  <ol ref="divLog"></ol>

export default {
  data() {
    return {
      activeComp: true
  beforeUpdate() {
    this.$refs.divLog.innerHTML += "<li>beforeUpdate: This happened just before the 'updated' hook.</li>";

#app > div {
  border: dashed black 1px;
  border-radius: 10px;
  padding: 10px;
  margin-top: 10px;
  background-color: lightgreen;
    <p>This is the component</p>
import { createApp } from 'vue'

import App from './App.vue'
import CompOne from './components/CompOne.vue'

const app = createApp(App)
app.component('comp-one', CompOne)