VueCompilerError: <template v-for> key should be placed on the <template> tag. code example

Example 1: vue js v-for array index

<ul>
  <li v-for="(val, index) in arr">
    <!-- Do something... -->
  </li>
</ul>

Example 2: v-for only getting one first value vuejs

<option v-for="(location, index) in locations" v-bind:value="location.id" v-bind:selected="index === 0">
  {{ location.from }} - {{ location.to }}
</option>