How to make login control function in vue.js

<template>
 <p class="login">
  <table width="100%" height="100%">
   <tr height="41"><td class="logintb" colspan="2"> </td></tr>
   <tr height="100%" class="loginbg">
    <td id="left_cont">
     <table width="100%" height="100%">
      <tr height="155"><td colspan="2"> </td></tr>
      <tr>
       <td width="20%" rowspan="2"> </td>
       <td width="60%">
        <table width="100%">
          <tr height="70"><td align="right"></td></tr>
          <tr height="274">
            <td valign="top" align="right">
              <img src="../../static/images/logo.png"/>
             </img/>
            </td>
          </tr>
        </table>
       </td>
       <td width="15%" rowspan="2"> </td>
      </tr>
      <tr><td colspan="2"> </td></tr>
     </table>
    </td>
    <td id="right_cont">
     <table height="100%">
      <tr height="30%"><td colspan="3"> </td></tr>
      <tr>
       <td width="30%" rowspan="5"> </td>
       <td valign="top" id="form">
          <table valign="top" width="50%">
            <tr><td colspan="2"><h4 style="letter-spacing:1px;font-size:16px;">管理后台</h4></td></tr>
            <tr><td>管理员：</td><td><input type="text" v-model.trim="username" value="" /></td></tr>
            <tr><td>密  码：</td><td><input type="password" v-model.trim="pwd" value="" /></td></tr>
            <!-- <tr><td>验证码：</td><td><input type="text" name="" value="" style="width:80px;"/></td></tr> -->
            <tr class="bt" align="center"><td> <input type="submit" @click="login" value="登陆" /></td><td> </td></tr>
          </table>
       </td>
       <td rowspan="5"> </td>
      </tr>
      <tr><td colspan="3"> </td></tr>
     </table>
    </td>
   </tr>
   <tr id="login_bot"><td colspan="2"><p>Copyright © 2017-{{getNowDate()}} Tujiawang</p></td></tr>
  </table>
 </p>
</template>
<script>
 import axios from 'axios'
 axios.defaults.withCredentials = true
 export default{
  data(){
   return {
    username:'',
    pwd:''
   }
  },
  methods: {
   login() {
    var params = new URLSearchParams();
    params.append('username', this.username);
    params.append('password', this.pwd);
    axios.post(this.HOST+'/home/system/login',params).then(res => {
      if(res.data.code ==1){
       sessionStorage.username = this.username;
       this.$router.push({path:'/main'})
      }else{
       alert('登录失败')
      }
    })
   },
   getNowDate(){
    var d = new Date();
    return d.getFullYear();
   }
  }
 }
</script>

import Vue from 'vue'
import Router from 'vue-router'
Vue.use(Router)
const routes = [
  {
    path: '/',
    redirect: '/login'
  },
  {
    path: '/login',
    name: 'login',
    component: (resolve)=>{require(['../components/Login'],resolve)}
  },
  {
    path: '/main',
    name: 'main',
    component: (resolve)=>{require(['../components/Home'],resolve)},
    redirect: 'main/info',
    children: [{
        path: 'info',
        meta: {
          id:-1
        },
        component: (resolve)=>{require(['../components/Main'],resolve)}
      }
    ]
  },
  {
    path: '/vips',
    name: 'vips',
    component: (resolve)=>{require(['../components/Home'],resolve)},
    redirect: 'vips/list',
    children: [{
        path: 'list',
        meta: {
          id:0
        },
        component: (resolve)=>{require(['../components/VipsList'],resolve)}
      },
      {
        path: 'detail',
        meta: {
          id:0
        },
        component: (resolve)=>{require(['../components/VipsDetail'],resolve)}
      },
      {
        path: 'userlog',
        meta: {
          id:0
        },
        component: (resolve)=>{require(['../components/UserLog'],resolve)}
      }
    ]
  }
];
const router = new Router({
  routes
});
/**
 * to:表示目标路由
 * from:表示来源路由
 * next:表示执行下一步操作
 */
router.beforeEach((to, from, next) => {
  if (to.path === '/login') { // 当路由为login时就直接下一步操作
    next();
  } else { // 否则就需要判断
    if(sessionStorage.username){ // 如果有用户名就进行下一步操作
     next()
    }else{
     next({path: '/login'}) // 没有用户名就跳转到login页面
    }
  }
})
export default router