title: Vue.js how to set :id prefix string?
body: <pre><code>class="tab-title" 
  v-on:click="tab" 
  v-for="(tabTitle,index) in tabTitleList"
  :id="index"
  </code></pre>
  
  <p>I found this example in an vue community, but in my situation, I want my "id"  has a prefix, not just a number.</p>
  
  <p>That is to say, if the index is 1, I want  <code>&lt;span id='sp_1'&gt;&lt;/span&gt;</code> instead of <code>&lt;span id='1'&gt;&lt;/span&gt;</code>.</p>