html

1.

		<ul class="header-list">
				<li v-cloak v-for="(item,index) in headerList" v-on:click="selectMainTheme(index)"><a href="java:;" :class="{'active':idx == index}">{{item.name}}</a></li>
		</ul>

js

	var app = new Vue({
			el:"#app",
			router,
			data:{
				m:"hello vue.js",
				active:'2',
				idx:'0',   //默认选择首页
				headerList:[
					{name:'首页1'},
					{name:'首页2'},
					{name:'首页3'},
					{name:'首页4'},
					{name:'首页5'},
					{name:'首页6'}
				]
			},
			methods:{
				// 1.选择
				selectMainTheme:function(index){
					console.log("selectMainTheme" + index);
					console.log("idx" + this.idx);
					this.idx = index;
				}
				// 
			}	

	});

2.运算表达式

  <i class="iconfont checkAllBtn" 
          :class="checkAll?'icon-checkboxround1':'icon-checkboxround0' " 
          v-model="checkAll" @click="choiceAll">全选</i>

3.

HTML代码：
<div :class="classA">Demo2</div>

Javascript代码：
data: {
  classA: 'class-a'  //当classA改变时将更新class
}

渲染后的HTML:
<div class="class-a">Demo2</div>

4.

HTML代码：
<div :class="{ 'class-a': isA, 'class-b': isB}">Demo4</div>

Javascript代码：
data: {
  isA: false,  //当isA改变时，将更新class
  isB: true    //当isB改变时，将更新class
}

渲染后的HTML:
<div class="class-b">Demo4</div>

参考文章：来源  https://www.cnblogs.com/big-snow/p/5718728.html