SOURCE

new Vue({
  el: '#main',
	// 定义属性，并设置初始值
	data: {
		active: 'home'
	},

	// 点击菜单使用的函数
	methods: {
		makeActive: function(item){
			// 模型改变，视图会自动更新
			this.active = item;
		}
	}
}）

<script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
<div id="main">
    <nav v-bind:class="active" v-on:click.prevent>
       <a href="#" class="home" v-on:click="makeActive('home')">首页
       <a href="#" class="projects" v-on:click="makeActive('projects')">案例</a>
       <a href="#" class="services" v-on:click="makeActive('services')">服务</a>
        <a href="#" class="contact" v-on:click="makeActive('contact')">联系</a>
     </nav>

    <p>您选择了 <b>{{active}} 菜单</b></p>
</div>

nav{
		display:inline-block;
		margin:60px auto 45px;
		background-color:#5597b4;
		box-shadow:0 1px 1px #ccc;
		border-radius:2px;
	}

	nav a{
		display:inline-block;
		padding: 18px 30px;
		color:#fff !important;
		font-weight:bold;
		font-size:16px;
		text-decoration:none !important;
		line-height:1;
		text-transform: uppercase;
		background-color:transparent;

		-webkit-transition:background-color 0.25s;
		-moz-transition:background-color 0.25s;
		transition:background-color 0.25s;
	}

	nav a:first-child{
		border-radius:2px 0 0 2px;
	}

	nav a:last-child{
		border-radius:0 2px 2px 0;
	}

	nav.home .home,
	nav.projects .projects,
	nav.services .services,
	nav.contact .contact{
		background-color:#e35885;
	}

	p{
		font-size:22px;
		font-weight:bold;
		color:#7d9098;
	}

	p b{
		color:#ffffff;
		display:inline-block;
		padding:5px 10px;
		background-color:#c4d7e0;
		border-radius:2px;
		text-transform:uppercase;
		font-size:18px;
	}