【腾讯云前端性能优化大赛】秒开的艺术：Hexo 博客首屏耗时优化实践

<link rel="stylesheet" href="/css/style/main.css">

<!-- 加载缓慢的 CSS -->
<link href="https://fonts.googleapis.com/css2?family=Noto+Sans+SC&display=swap" rel="stylesheet">

<!-- CSS 加载时不会阻塞页面渲染 -->
<link href="https://fonts.googleapis.com/css2?family=Noto+Sans+SC&display=swap" rel="stylesheet" media="only x" onload="this.onload=null;this.media='all'">

const hasha = require("hasha");
const minimatch = require("minimatch");

function stream2buffer(stream) {
  return new Promise((resolve, reject) => {
    const _buf = [];
    stream.on("data", (chunk) => _buf.push(chunk));
    stream.on("end", () => resolve(Buffer.concat(_buf)));
    stream.on("error", (err) => reject(err));
  });
}

const readFileAsBuffer = (filePath) => {
  return stream2buffer(hexo.route.get(filePath));
};

const readFileAsString = async (filePath) => {
  const buffer = await readFileAsBuffer(filePath);
  return buffer.toString();
};

const parseFilePath = (filePath) => {
  const parts = filePath.split("/");
  const originalFileName = parts[parts.length - 1];

  const dotPosition = originalFileName.lastIndexOf(".");

  const dirname = parts.slice(0, parts.length - 1).join("/");
  const basename =
    dotPosition === -1
      ? originalFileName
      : originalFileName.substring(0, dotPosition);
  const extension =
    dotPosition === -1 ? "" : originalFileName.substring(dotPosition);

  return [dirname, basename, extension];
};

const genFilePath = (dirname, basename, extension) => {
  let dirPrefix = "";
  if (dirname) {
    dirPrefix += dirname + "/";
  }

  if (extension && !extension.startsWith(".")) {
    extension = "." + extension;
  }

  return dirPrefix + basename + extension;
};

const getRevisionedFilePath = (filePath, revision) => {
  const [dirname, basename, extension] = parseFilePath(filePath);
  return genFilePath(dirname, `${basename}.${revision}`, extension);
};

const revisioned = (filePath) => {
  return getRevisionedFilePath(filePath, `!!revision:${filePath}!!`);
};

hexo.extend.helper.register("revisioned", revisioned);

hexo.extend.filter.register("stylus:renderer", function (style) {
  style.define("revisioned", (node) => {
    return new style.nodes.String(revisioned(node.val));
  });
});

const calcFileHash = async (filePath) => {
  const buffer = await stream2buffer(hexo.route.get(filePath));
  return hasha(buffer, { algorithm: "sha1" }).substring(0, 8);
};

async function replaceRevisionPlaceholder() {
  const options = hexo.config.new_revision || {};
  const include = options.include || [];
  const enable = !!options.enable || false;

  if (!enable) {
    return false;
  }

  const hashPromiseMap = {};
  const hashMap = {};
  const doHash = (filePath) =>
    calcFileHash(filePath).then((hash) => {
      hashMap[filePath] = hash;
    });

  await Promise.all(
    hexo.route.list().map(async (path) => {
      const [, , extension] = parseFilePath(path);
      if (![".css", ".js", ".html"].includes(extension)) {
        return;
      }

      let fileContent = await readFileAsString(path);

      const regexp = /\\.!!revision:([^\\)]+?)!!/g;
      const matchResult = [...fileContent.matchAll(regexp)];
      if (matchResult.length) {
        const hashTaskList = [];

        // 异步获取文件 hash
        matchResult.forEach((group) => {
          const filePath = group[1];
          if (!(filePath in hashPromiseMap)) {
            hashPromiseMap[filePath] = doHash(filePath);
          }
          hashTaskList.push(hashPromiseMap[filePath]);
        });

        // 等待全部 hash 完成
        await Promise.all(hashTaskList);

        // 替换 placeholder
        fileContent = fileContent.replace(regexp, function (match, filePath) {
          if (!(filePath in hashMap)) {
            throw new Error("file hash not computed");
          }
          return "." + hashMap[filePath];
        });

        hexo.route.set(path, fileContent);
      }
    })
  );

  await Promise.all(
    hexo.route.list().map(async (path) => {
      for (let i = 0, len = include.length; i < len; i++) {
        if (minimatch(path, include[i])) {
          return doHash(path);
        }
      }
    })
  );

  await Promise.all(
    Object.keys(hashMap).map(async (filePath) => {
      hexo.route.set(
        getRevisionedFilePath(filePath, hashMap[filePath]),
        await readFileAsBuffer(filePath)
      );
      hexo.route.remove(filePath);
    })
  );
}

hexo.extend.filter.register("after_generate", replaceRevisionPlaceholder);

function loadComment() {
  // 插入 script 标签
}

if ('IntersectionObserver' in window) {
  const observer = new IntersectionObserver(function (entries) {
    // 浏览器视口与监听的元素有交集时会触发该回调
    if (entries[0].isIntersecting) {
      // 触发 JS 加载
      loadComment();
      // 取消监听，避免重复触发这个回调
      observer.disconnect();
    }
  }, {
    // 回调触发的阈值，这里是 10% 的部分出现在屏幕中时会触发以上的回调
    threshold: [0.1],
  });
  observer.observe(document.getElementById('comment'));
} else {
  // 浏览器不支持 IntersectionObserver，立即触发 JS 加载
  loadComment();
}

@font-face {
  font-family: 'Noto Serif SC';
  font-style: normal;
  font-weight: 400;
  font-display: swap;
  src: url("./font/logo.woff2") format("woff2");
  unicode-range: U+7535,U+8111,U+661F,U+4EBA;
}

const fontCarrier = require('font-carrier');
const transFont = fontCarrier.transfer('./NotoSerifSC-Regular.otf');
transFont.min('电脑星人');
transFont.output({
  path: './logo'
});