a simple cache middleware wrapper for nodejs web server

cache.js

// cache.js
const debug = console.log;
const nextTick = process.nextTick;

const CACHE = {
  check(key, req, res) {
    if (this._cache[key]) {
      debug('cache %s hit', key);
      nextTick(() => {
        res.end(this._cache[key]);
      });

      return;
    }

    if (this._queue[key]) {
      debug('batch operation in queue for key %s', key);
      this._queue[key].push((text) => {
        res.end(text);
      });
      return;
    }

    this._queue[key] = [(text) => {
      res.end(text);
    }];

    setTimeout(() => {
      this._cache[key] = "ABCDEFG"; // a large long text

      // 缓存过期
      setTimeout(() => {
        delete this._cache[key];
      }, 30 * 1000);

      const queue = this._queue;
      const q = queue[key];
      queue[key] = null;
      q.forEach(cb => cb(this._cache[key]));
    }, 1000);
  },
  _cache: {},
  _queue: {}
}

// HOW TO USE?
// should only work for API request
const http = require('http');
http.createServer(function (req, res) {
  const key = req.url;
  console.log(key);
  // key can be a hash of url and query data
  CACHE.check(key, req, res);
  return;
}).listen(3040);