在vue项目中使用Nprogress.js进度条的方法

$ bower install --save nprogress
$ npm install --save nprogress

import NProgress from 'nprogress'
import 'nprogress/nprogress.css'

NProgress.start(); 
NProgress.done();

router.beforeEach((to, from, next) => {
if (to.path == '/login') {
 sessionStorage.removeItem('username');
 }
let user = sessionStorage.getItem('username');
if (!user && to.path != '/login') {
 next({path: '/login'})
 } else {
 NProgress.start();
 next()
 }
});
router.afterEach(transition => {
 NProgress.done();
});