SPA 如何达到 SSR 一样的秒开效果？

const generate = () => {}

class Renderer {}

const getHtml = async ({ userAgent, onRequest, url }) => {
  const browser = await puppeteer.launch({ headless: true, args: ['--no-sandbox', '--disable-setuid-sandbox'] }) // 启动无头浏览器

  const page = await browser.newPage()
  await page.setViewport({ width: 375, height: 812 })
  if (userAgent) await page.setUserAgent(userAgent)
  // 页面实例上下文中执行的方法
  await page.evaluateOnNewDocument(() => (window['_prerender_'] = 'prerender'))
  // 启用请求拦截器
  await page.setRequestInterception(true)
  // 监听请求
  page.on('request', (request) => onRequest?.({ request, pageUrl: url, page }))

  await page.goto(url)
  // 页面实例上下文中执行的方法
  await page.evaluate(observeRender) // 默认5000ms页面加载完成
  const content = await page.content()
  await page.close()
  return content
}

const cssContent = {}

const onRequest = asycn ({ request }) => {
  const body = await read(url)
  if (cssInline && filename.endsWith('.css')) {
    const byteLength = body.byteLength
    const { maxSize = Infinity, exclude, include } = cssInline

    if (!(byteLength > maxSize || exclude?.test(filename)) && (!include || include.test(filename))) {
      // 把css 先存起来
      cssContent[filename] = body.toString()
    }
  }
  
  return request.respond({
    status: 200,
    body,
  })
}

const generate = async (config: GenerateConfigParams) => {
  const generate = async (config: GenerateConfigParams) => {
    const {
      sourceDir, //源文件目录
      staticDir = sourceDir, // 静态资源打包目录
      pages, // 页面路由
      baseUrl = 'https://m.dewu.com',
      cdn = '',
      userAgent = DWUA,
      postProcess, // 处理生成后的html
      inject,
    } = config
    const mutation = typeof config.mutation === 'string' ? [config.mutation] : config.mutation
    const renderer = new Renderer()
    renderer.pages = pages
    renderer.baseUrl = baseUrl
    renderer.userAgent = userAgent
    const sourceHTMLPath = join(sourceDir, 'index.html')
    
    renderer.postProcess = ({ html, page }) => {
      if (mutation) {
        const dom = new JSDOM(sourceHTML)
        const newDom = new JSDOM(html)
        // 将新的HTML替换老的HTML
        mutation.forEach((mutation) => {
          const oldNode = dom.window.document.querySelector(mutation) as HTMLElement
          const newNode = newDom.window.document.querySelector(mutation) as HTMLElement
          if (oldNode) {
            oldNode.innerHTML = newNode?.innerHTML ?? ''
          }
        })
        
        // 将所有通过link标签引入的css资源移除，换成style标签包裹的内联CSS
        const links = newDom.window.document.querySelectorAll('link')
        for (const link of links) {
          const originHref = link.getAttribute('href') ?? ''
          const content = cssContent[originHref.split('/').pop() ?? '']
          if (content) {
            const newStyle = dom.window.document.createElement('style')
            newStyle.innerHTML = content
            newStyle.setAttribute('data-href', originHref)
            newStyle.setAttribute('data-css', 'inline')
            dom.window.document.head.appendChild(newStyle)
            const link = dom.window.document.querySelector(`link[href="${originHref}"]`)
            if (link) {
              link.parentElement?.removeChild(link)
            }
          }
        }

        html = dom.serialize()
      }
      
      return {
        html,
        page,
      }
    }

    renderer.onRequest = () => {
    // 上面的 onRequest 函数 ....
    }
  }
}

@keyframes bigScale {
  0% {
    opacity: 0;
    transform: scale(0.95);
  }

  to {
    transform: scale(1);
    opacity: 1;
  }
}

@keyframes smallScale {
  0% {
    transform: scale(1);
    opacity: 1;
  }

  to {
    transform: scale(0.95);
    opacity: 0;
  }
}

.squareInCenter {
  animation: 0.3s linear 0s 1 normal forwards running bigScale;
}

.squareOutCenter {
  animation: 0.3s linear 0s 1 normal forwards running smallScale;
}