title: difference between v-for structures
body: <p>Could someone explain what is the difference between those 2 <em><strong>v-for</strong></em> structures:</p>
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
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  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;li v-for="item in items" :key="item"&gt;
  &lt;/li&gt;</code></pre>
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  </p>
  <p>and</p>
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;li v-for="(item, i) in items" :key="i"&gt;
  &lt;/li&gt;</code></pre>
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  </p>