0-cache-second-try.js

0-cache-second-try.js

// our own in memory database
var users = {
  'alex': { user: 'alex', age: 27 },
  'john': { user: 'johndoe', age: 34 }
};

// async function
var getUserFromDb = function getUserFromDb(id, callback) {
  var min = 1000;
  var max = 2000;
  var randomTimeout = Math.floor(Math.random() * (max - min + 1)) + min;

  setTimeout(function() {
    callback(null, users[id] || null);
  }, randomTimeout);
};

var cachify = function cachify(originalFn, getFromCache) {
  return function(id, callback) {
    // here we will first try to grab the result from the cache
    // in case it doesn't exist -> call the original function
    getFromCache(id, function(err, result) {
      // handle error -> if (err) ..

      if (result !== null && typeof result !== 'undefined') {
        callback(null, result);
      } else {
        originalFn(id, callback);
      }
    });
  };
};

var getResultFromCache = function getResultFromCache(id, cb) {
  setTimeout(function() {
    cb(null, users[id] || null);
  }, 0);
};

// Example:
// this takes between 1-2 seconds to get the result
console.time('database');
getUserFromDb('alex', function(err, user) {
  if (err) { throw err; }

  console.log('directly hitting the database:', user);
  console.timeEnd('database');
});

// this should be much faster
console.time('cache');
var cachedAsyncFunction = cachify(getUserFromDb, getResultFromCache);
cachedAsyncFunction('alex', function(err, result) {
  if (err) { throw err; }

  console.log('from cache:', result);
  console.timeEnd('cache');
});