Simple Node.js Cache Module

cache.js

module.exports = function() {
  var cache = {},
      expires = 1000 * 60 * 60; // default expiration, 1 hour

  var isValid = function(key) {
    if(!cache.hasOwnProperty(key) || cache[key].expires <= Date.now()) {
      return false;
    }

    return true;
  };

  var set = function(key, value, expiration) {
    expiration = expiration || expires;

    cache[key] = {
      expires: Date.now() + expiration,
      data: value
    };
  };

  var get = function(key) {
    if(!cache.hasOwnProperty(key)) {
      return null;
    }

    return cache[key].data;
  };

  return {
    isValid: isValid,
    set: set,
    get: get
  };
};