vue 之watch 监听路由地址的改变

<!DOCTYPE html>
<html >

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <script src="./js/vue.js"></script>
  <script src="./js/vue-router-3.0.1.js"></script>
</head>

<body>
  <div >

    <!-- 如果在路由中,使用查询字符串,则不需要修改 路由匹配规则 -->
    <router-link to="/login">登录</router-link>
    <router-link to="/register">注册</router-link>

    <!-- 容器 -->
    <router-view></router-view>
  </div>

  <script>
    var login = {
      // this默认指当前组件实例,在插值表达式中this可以省略
      template: '<h1>登录组件</h1>',
    };

    var register = {
      template: '<h1>注册组件</h1>'
    }

    var router = new VueRouter({
      routes: [
        { path: '/login',component: login},
        { path: '/register',component: register},
      ]
    })

    //创建Vue实例,得到 ViewModel
    var vm = new Vue({
      el: '#app',
      data: {},
      methods: {},
      router: router, //将路由规则挂载到vm实例中
      watch:{
        // 监听 this.$route.path     watch监听非DOM元素的改变
        '$route.path':function(newVal,oldVal){
          // console.log(newVal + '---' +  oldVal);
          if(newVal === '/login'){
            console.log('欢迎进入登录页面');
          }else if(newVal === '/register'){
            console.log('欢迎进入注册页面');
          }
        }
      }
    });
  </script>
</body>

</html>