[Vuejs]-Vuejs v-for loop breaks column layout

//example 1
<ul>
  <li v-for="(item,index) in items">{item.name}</li>
</ul>

//example 2
<div class="item">
  <acticle v-for="(item,index) in items">
      <h2>{item.name}</h2>
      <span>date:{item.date}</span>
  </acticle>
</div>