express js middleware LRU

middleware.v3.js

function evictLeastRecentlyUsed(cacheDir, maxSize, logger) {
  getFolderSize(cacheDir, (err, size) => {
    if (err) {
      throw err;
    }

    if (size >= maxSize) {
      try {
        // find least recently used file
        const leastRecentlyUsed = findLeastRecentlyUsed(cacheDir);

        // and delete it
        const { dir } = path.parse(leastRecentlyUsed.path);
        fs.unlinkSync(leastRecentlyUsed.path);
        fs.rmdirSync(dir);

        if (logger) {
          logger.info(`Evicted ${leastRecentlyUsed.path} from cache`);
        }

        evictLeastRecentlyUsed(cacheDir, maxSize, logger);
      } catch (e) {
        logger.error(e);
      }
    }
  });
}

function findLeastRecentlyUsed(dir, result) {
  let files = fs.readdirSync(dir);
  result = result || { atime: Date.now(), path: "" };

  files.forEach(file => {
    const newBase = path.join(dir, file);

    if (fs.statSync(newBase).isDirectory()) {
      result = findLeastRecentlyUsed(newBase, result);
    } else {
      const { atime } = fs.statSync(newBase);

      if (atime < result.atime) {
        result = {
          atime,
          path: newBase
        };
      }
    }
  });

  return result;
}