const router = new VueRouter({
routes: [...],
scrollBehavior (to, from, savedPosition) {
 // return 期望滾動到哪個的位置
}
}) 

{ x: number, y: number }
{ selector: string } 

<div id="app">
  <h1>滾動行為</h1>
  <ul>
    <li><router-link to="/">首頁</router-link></li>
    <li><router-link to="/foo">導航</router-link></li>
    <li><router-link to="/bar">關于</router-link></li>
    <li><router-link to="/bar#an1">紅色頁面</router-link></li>
    <li><router-link to="/bar#an2">藍色頁面</router-link></li>
  </ul>
  <router-view></router-view>
</div>
<script>
  var Home = {
    template:"<div>home</div>"
  }
  var Foo = {
    template:"<div>foo</div>"
  }
  var Bar = {
    template:
      `
        <div>
          bar
          <div style="height:500px;background: yellow;"></div>
          <p id="an1" style="height:500px;background: red;">紅色頁面</p>
          <p id="an2" style="height:300px;background: blue;">藍色頁面</p>
        </div>
      `
  }

  var router = new VueRouter({
    mode:"history",
    //控制滾動位置
    scrollBehavior (to, from, savedPosition) {
      //判斷如果滾動條的位置存在直接返回到當前位置，否者返回到起點
      if (savedPosition) {
        return savedPosition
      } else {
        if (to.hash) {
          return {selector: to.hash}
        }
      }
    },
    routes:[
      {
        path:"/",component:Home
      },
      {
        path:"/foo",component:Foo
      },
      {
        path:"/bar",component:Bar
      }
    ]
  });
  var vm = new Vue({
    el:"#app",
    router
  });
</script>