vue实现点击Button效果

<ul class="top_bar">
    <li class="top_cell"
        v-for="cell in 5"
        :class="{ 'active': cell === selected }"
        @click="choose(cell)">
        {{cell}}
    </li>

</ul>

new Vue({
    el:'.top_bar',
    data:{
        selected: null
    },
    methods:{
        choose:function (index) {
            this.selected = index
        }
    }
});