document.querySelector is null vuejs laravel

Question

I've tried to find references, but haven't solved it, I have the code below..

why document.querySelector('meta[name="user_id"]').content

Uncaught TypeError: document.querySelector(...) is null

this my code

html

<div class="card">
  <div class="card-body card-message" id="card-message-scroll">
    <ul v-if="isActive != null" class="list-group list-group-flush">
      <div v-for="(message, index) in messages" v-bind:key="index">
        <li v-if="message.from_id != {{ auth()->user()->id }}" class="list-group-item">
          <div class="list-message-item">
            <div class="media">
              <img class="mr-3 rounded-sm rounded-circle" :src="message.avatar" alt="profile">
              <div class="media-body">
                <div class="alert alert-primary mb-0"> @{{ message.content }}
                </div>
                <small>
                  <i>@{{ new Date(message.created_at).toLocaleDateString()}}</i>
                </small>
              </div>
            </div>
          </div>
        </li>
        <li v-else class="list-group-item">
          <div class="list-message-item right">
            <div class="alert alert-secondary mb-0"> @{{ message.content }}
            </div>
            <small class="float-right">
              <i>@{{ new Date(message.created_at).toLocaleDateString()}}</i>
            </small>
          </div>
        </li>
      </div>
    </ul>
    <h5 v-else class="text-center">Pilih user untuk mengirim pesan</h5>
  </div>
</div>

this my app.js

new Vue({
    el: '#app',
    data: {
        id: document.querySelector('meta[name="user_id"]').content,
    },
    mounted() {
    },
    methods: {
       
        scrollToEnd: function () {
            let container = this.$el.querySelector("#card-message-scroll");
            container.scrollTop = container.scrollHeight;
        }
    },
    watch: {
        messages: _.debounce( function() {
            this.scrollToEnd()
        }, 10),
    }
})

Uncaught TypeError: document.querySelector(...) is null

why ?