Vue

HTML

<div id="app">
  <ol>
    <li :class="del === key ? 'del' : ''" v-for="(todo, key) in todos" :key="key" @click="clickHandler(key)">{{ todo.text }}</li>
  </ol>
</div>

CSS

li {
  padding: 10px;
}
.del {
  background: #ff0000;
}

Vue

new Vue({
  el: "#app",
  data: {
    todos: [
      { text: "Learn JavaScript" },
      { text: "Learn Vue" },
      { text: "Play around in JSFiddle" },
      { text: "Build something awesome" }
    ],
    del: null
  },
  methods: {
  	clickHandler (index) {
    console.log(index)
    	let todos = document.querySelectorAll('li')
      this.del = index
      setTimeout(() => {
      	this.todos.splice(index, 1)
      }, 1000)
    }
  }
})