JSFiddle - React, Tailwind, and code Playground

HTML

<div id="app">
 <ul >
 <li :class="className" v-for="lis in lista">list {{ lis }}</li>
 </ul>
 <button @click="adicionaritem">
 Adiciona item
 </button>
</div>

CSS

li {
  transition: background .3s;
}
li:last-child.active {
   background: yellow
}

JavaScript

new Vue({
	el: '#app',
  data: () => ({
  	className: '',
    lista:5
  }),
  methods: {
  	add() {
    	this.className = 'active'
      window.setTimeout(e => this.className = '', 2000)
    },
    adicionaritem(){
    this.lista +=1
    this.add()
    }
  }
})