Nuxt/lib/app/server.js

const debug = require('debug')('nuxt:render')
import Vue from 'vue'
import { pick } from 'lodash'
import { app, router<%= (store ? ', store' : '') %> } from './index'
import { getMatchedComponents, getContext } from './utils'

const isDev = process.env.NODE_ENV !== 'production'
const _app = new Vue(app)

// 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)

  // Add route to the context
  context.route = router.currentRoute
  // Add meta infos
  context.meta = _app.$meta()
  // Add store to the context
  <%= (store ? 'context.store = store' : '') %>

  // Nuxt object
  context.nuxt = { data: [], error: null<%= (store ? ', state: null' : '') %> }

  <%= (isDev ? 'const s = isDev && Date.now()' : '') %>
  // Call data & fecth hooks on components matched by the route.
  let Components = getMatchedComponents(context.route)
  if (!Components.length) {
    context.nuxt.error = _app.error({ statusCode: 404, message: 'This page could not be found.', url: context.route.path })
    <%= (store ? 'context.nuxt.state = store.state' : '') %>
    return Promise.resolve(_app)
  }
  return Promise.all(Components.map((Component) => {
    let promises = []
    if (Component.data && typeof Component.data === 'function') {
      Component._data = Component.data
      var promise = Component.data(getContext(context))
      if (!(promise instanceof Promise)) promise = Promise.resolve(promise)
      promise.then((data) => {
        Component.data = () => data
      })
      promises.push(promise)
    } else {
      promises.push(null)
    }
    if (Component.fetch) {
      promises.push(Component.fetch(getContext(context)))
    }
    return Promise.all(promises)
  }))
  .then((res) => {
    <% if (isDev) { %>
      debug('Data fetch ' + context.req.url + ': ' + (Date.now() - s) + 'ms')
    <% } %>
    // datas are the first row of each
    context.nuxt.data = res.map((tab) => tab[0])
    <%= (store ? '// Add the state from the vuex store' : '') %>
    <%= (store ? 'context.nuxt.state = store.state' : '') %>
    return _app
  })
  .catch(function (error) {
    context.nuxt.error = _app.error(error)
    <%= (store ? 'context.nuxt.state = store.state' : '') %>
    return _app
  })
}