javascript - vuejs的extend方法在vue2中不知道是否还有，解释一下

Answer 1

Migrate from Vue 1.x to 2.x
Migrate from Vue Router 0.7.x to 2.x
Migrate from Vuex 0.6.x to 1.0(2.0)

Answer 2

Not much change in writing style.
We provide you with two writing methods, you can use them according to your situation

const router = new VueRouter({ .... })

...
// 第一种写法
const app = new Vue({
    router,
    ...App // 扩展
}).$mount('#app')

// 第二种
new Vue({
  el: '#app',
  router,
  template: '<App/>',
  components: { App }
})

In additionVue.extend is to use the basic Vue constructor to create a "subclass". The parameter is an object containing the component's options.
Look at the source code and it will be clear at a glance. global-api/extend