const app = Vue.createApp({
  data() {
    return {
      isLoggedIn: true,
      avatarUrl: 'https://example.com/avatar.png'
    }
  },
  methods: {
    logOut() {
      this.isLoggedIn = false
    }
  }
})

app.mount('#app')

<!-- template -->
<div id="app">
  <img v-bind:src="avatarUrl" alt="User avatar" />
  <p v-if="isLoggedIn">Welcome back!</p>
  <p v-else>Please sign in.</p>
  <button v-on:click="logOut">Log out</button>
</div>