gistfile1.txt

<div id="lalala">
  <div v-for="(element, key) in list" :key="key">
    <button @click="changeFlag">{{ getDate() }}</button>
  </div>
  <div v-if="flag">LALALA</div>
</div>

<script>
let lalala = new Vue({
  el: '#lalala',
  data: {
    list: ['lalala', 'lalala 2'],
    flag: false
  },
  methods: {
    getDate() {
      return Date();
    },
    changeFlag() {
      this.flag = true;
    }
  }
});
</script>