vue

<div class="user">
    <input type="text" placeholder="Name" v-model="name" @keypress="setTitle">
    <h2>Username: {{ title }}</h2>
</div>

// Vue code You have to code this on javascript file
const user = {
  data() {
    return {
      name: "",
      title: ""
    }
  },
  methods: {
  setTitle(e) {
      if (e.keyCode == 13) {
        this.title = this.name
      }
    }
  }
}

Vue.createApp(user).mount("#user");