v-for对应项添加active类

1.点击时候让当前元素的class判断条件为真

<ul>
    <li :class="{'active': index === selected }" v-for="(item, index) in list" @click="choose(index)"></li>
</ul>

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