Caching in Javascript

cachedWorkerInfo.js

cachedWorkerInfo = {
  cacheTimeSecs: 60 /* 60 seconds == 1 minute */
, timeoutId : 0
, get: function (workerId, sql) { return this._checkCached(workerId, sql) && this[workerId]['sqlResults']}
, put: function (workerId, sql, sqlResults) { return this[workerId] = {'sql': sql, 'sqlResults': sqlResults, 'queryTime': new Date()}; }
, scheduleCleanup : function() { if (!cachedWorkerInfo.timeoutId) cachedWorkerInfo.timeoutId = setTimeout(cachedWorkerInfo.clear, cachedWorkerInfo.cacheTimeSecs * 2 * 1000); /* called maximum of once per 2 minutes */ }
, clear : function clear(everything) { var that=cachedWorkerInfo, now = new Date(); for (var x in that) {if (typeof that[x] != "function" && null != that[x] && null != that[x].queryTime) {if (true == everything || false == that._stillValid(x, now)) {delete that[x] ;}}} that.timeoutId = 0; }
, _checkCached: function (workerId,sql) { return this[workerId] != null && this[workerId]['sql'] === sql && this._stillValid(workerId, new Date()); }
, _stillValid: function (workerId, now) { return now - this[workerId]['queryTime'] < this.cacheTimeSecs * 1000; }
}; 


// Typical usage (you define doSqlQuery):


function get_cached_worker_id(workerId, sql, doSqlQuery, verbose) {
   var results = cachedWorkerInfo.get(workerId, sql);
   if (!results) { 
      results = doSqlQuery(sql); 
      cachedWorkerInfo.put(workerId, sql, results); 
      cachedWorkerInfo.scheduleCleanup(); /* delete old entries 2 minutes after first query */
   }
   if (verbose && results != cachedWorkerInfo.get(workerId, sql)) {
      alert("Could not cache " + sql);
   }
   return results;
}


var result, workerId = 30, sql = "SELECT * from worker where worker_id = '30';", verbose=true;
if (!window.doSqlQuery) doSqlQuery = function(sql) { return sql; /* usually ajax request to MySQL */ }
result = get_cached_worker_id(workerId, sql, doSqlQuery, verbose);
alert(result);