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詳解webpack + react + react-router 如何實(shí)現(xiàn)懶加載

更新時(shí)間：2017年11月20日 11:15:47 作者：M.M.F

這篇文章主要介紹了詳解webpack + react + react-router 如何實(shí)現(xiàn)懶加載,具有一定的參考價(jià)值，感興趣的小伙伴們可以參考一下。

在 Webpack 1 中主要是由bundle-loader進(jìn)行懶加載，而 Webpack 2 中引入了類似于 SystemJS 的System.import語法，首先我們對(duì)于System.import的執(zhí)行流程進(jìn)行簡單闡述：

Webpack 會(huì)在編譯過程中掃描代碼庫時(shí)將發(fā)現(xiàn)的System.import調(diào)用引入的文件及其相關(guān)依賴進(jìn)行單獨(dú)打包，注意，Webpack 會(huì)保證這些獨(dú)立模塊及其依賴不會(huì)與主應(yīng)用的包體相沖突。
當(dāng)我們?cè)L問到這些獨(dú)立打包的組件模塊時(shí)，Webpack 會(huì)發(fā)起 JSONP 請(qǐng)求來抓取相關(guān)的包體。
System.import 同樣也是 Promise，在請(qǐng)求完成之后System.import會(huì)將抓取到的模塊作為參數(shù)傳入then中的回調(diào)函數(shù)。
如果我們重復(fù)訪問已經(jīng)加載完畢的模塊，Webpack 不會(huì)重復(fù)執(zhí)行抓取與解析的過程。

而 React Router 路由的懶加載實(shí)際上分為動(dòng)態(tài)路由與與懶加載兩步，典型的所謂動(dòng)態(tài)路由配置如下：

/**
 * <Route path="/" component={Core}>
 *  <IndexRoute component={Home}/>
 *  <Route path="about" component={About}/>
 *  <Route path="users" component={Users}>
 *  <Route path="*" component={Home}/>
 * </Route>
 */
export default {
 path: '/', 
 component: Core,
 indexRoute: { 
  getComponent(location, cb) {
    ...
  },
 },
 childRoutes: [
  {
   path: 'about', 
   getComponent(location, cb) {
    ...
   },
  },
  {
   path: 'users', 
   getComponent(location, cb) {
    ...
   },
  },
  {
   path: '*', 
   getComponent(location, cb) {
    ...
   },
  },
 ],
};

正常打包

import IndexPage from './views/app.jsx'
import AboutPage from './views/about.jsx'
export default function({history}) {
  return (
    <Router history={history}>
      <Route path="/" component={IndexPage} />
      <Route path="/about" component={AboutPage} />
    </Router>
  )
}

這是一個(gè)正常打包的路由寫法, 如果需要分割代碼, 我們需要改造下路由, 借助getComponent和require.ensure

webpack 代碼分割

export default function({history}) {
  return (
    <Router history={history}>
      <Route path="/" getComponent={(location, callback) => {
        require.ensure([], function(require) {
          callback(null, require('./HomePage.jsx'))
        })
      }} />
      <Route path="/about" getComponent={(location, callback) => {
        require.ensure([], function(require) {
          callback(null, require('./AboutPage.jsx'))
        })
      }} />
    </Router>
  )
}

這樣看來代碼有點(diǎn)累, 我們稍微改造下

const home = (location, callback) => {
 require.ensure([], require => {
  callback(null, require('./HomePage.jsx'))
 }, 'home')
}

const about = (location, callback) => {
 require.ensure([], require => {
  callback(null, require('./AboutPage.jsx'))
 }, 'about')
}
export default function({history}) {
  return (
    <Router history={history}>
      <Route path="/" getComponent={home}></Route>
      <Route path="/about" getComponent={about}></Route>
    </Router>
  )
}

這樣看起來是不是簡潔了很多

注意: 由于webpack的原因, 如果直接require('./AboutPage.jsx')不能正常加載, 請(qǐng)嘗試require('./AboutPage.jsx').default

webpack2 代碼分割

上面的代碼看起來好像都是webpack1的寫法, 那么webpack2呢?

webpac2就需要借助System.import了

export default function({history}) {
  return (
    <Router history={history}>
      <Route path="/" getComponent={(location, callback) => {
        System.import('./HomePage.jsx').then(component => {
          callback(null, component.default || component)
        })
      }} />
      <Route path="/about" getComponent={(location, callback) => {
        System.import('./AboutPage.jsx').then(component => {
          callback(null, component.default || component)
        })
      }} />
    </Router>
  )
}

我們一樣可以把上面的代碼優(yōu)化一下

const home = (location, callback) => {
  System.import('./HomePage.jsx').then(component => {
    callback(null, component.default || component)
  })
}
const about = (location, callback) => {
  System.import('./AboutPage.jsx').then(component => {
    callback(null, component.default || component)
  })
}

export default ({ history }) => {
  return (
    <Router history={history}>
      <Route name="home" path="/" getComponent={home} />
      <Route name="about" path="/about" getComponent={about} />
    </Router>
  )
}

webpack2 + dva 實(shí)現(xiàn)路由和 models 懶加載

const routerThen = (app, callback, [component, model]) => {
  app.model(model.default || model)
  callback(null, component.default || component)
}

export default ({ history, app }) => {
  return (
    <Router history={history}>
      <Route name="home" path="/" getComponent={(location, callback) => {
        Promise.all([
          System.import('./views/app.jsx'),
          System.import('./models/topics')
        ]).then(routerThen.bind(null, app, callback))
      }} />
      <Route name="article" path="/article/:id" getComponent={(location, callback) => {
        Promise.all([
          System.import('./views/article.jsx'),
          System.import('./models/topic')
        ]).then(routerThen.bind(null, app, callback))
      }} />
    </Router>
  )
}

以上就是本文的全部內(nèi)容，希望對(duì)大家的學(xué)習(xí)有所幫助，也希望大家多多支持腳本之家。

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