1、按需加载；（1）const Shop = () => import('@/page/shop/Shop')
{
path: '/shop',
name: Shop,
// component: resolve => require(['../page/shop/Shop'], resolve)
component: Shop
}可以生成多个js文件
（2）component: resolve => require(['../page/index/Index'], resolve)，这种方法所有的组件生成一个js文件
