server-entry.js

import Vue from 'vue'
import { app, router, store } from './app'

const _app = new Vue(app)

const isDev = process.env.NODE_ENV !== 'production'

// This exported function will be called by `bundleRenderer`.
// This is where we perform data-prefetching to determine the
// state of our application before actually rendering it.
// Since data fetching is async, this function is expected to
// return a Promise that resolves to the app instance.
export default context => {
  // set router's location
  router.push(context.url)

  const s = isDev && Date.now()

  // Call preFetch hooks on components matched by the route.
  // A preFetch hook dispatches a store action and returns a Promise,
  // which is resolved when the action is complete and store state has been
  // updated.
  return Promise.all(router.getMatchedComponents().map(component => {
    if (component.preFetch) {
      return component.preFetch(store)
    }
  })).then(() => {
    isDev && console.log(`data pre-fetch: ${Date.now() - s}ms`)
    // After all preFetch hooks are resolved, our store is now
    // filled with the state needed to render the app.
    // Expose the state on the render context, and let the request handler
    // inline the state in the HTML response. This allows the client-side
    // store to pick-up the server-side state without having to duplicate
    // the initial data fetching on the client.
    context.initialState = store.state
    return _app
  })
}