title: Vue.js throws multiple warnings: Invalid prop: type check failed for prop "items". Expected Array, got String with value ""
body: <p>I am using <code>vue-cli</code> for the front-end and <code>express</code> for the backend. The processing time for my backend data is 1.7 sec and if I do the request under <code>mounted ()</code>, vue already has read the <code>data ()</code> and gives me warnings, that it is expecting other type and can't do sort etc.</p>
  
  <p><strong>Is there a way to do this without the warnings?</strong></p>
  
  <p>This my html part:</p>
  
  <pre><code>   &lt;v-data-table
          class="ownstyle"
          :headers="headers"
          :items="orders"
      &gt;
          &lt;template slot="items" slot-scope="props"&gt;
              &lt;td &gt;{{ props.item.value1 }}&lt;/td&gt;
              &lt;td &gt;{{ props.item.value2 }}&lt;/td&gt;
              ...
          &lt;/template&gt;
      &lt;/v-data-table&gt;
  </code></pre>
  
  <p>And here is the script part:</p>
  
  <pre><code>data () {
      return {
          headers: [
              { text: 'name1', value: 'value1', ...},
              { text: 'name2', value: 'value2', ...},
              ...
          ],
          orders: ''
      }
  },
  
  mounted () {
      ApiService.orders().then(
          response =&gt; (this.orders = response.data))
  }
  </code></pre>