Javascript / Node.js / MongoDB callback example

Callback example

// Function with callback

var getPayerIDs = function(db, callback) {
       console.log("is db null?:" + (db == null));
       var condition = new Object();
       condition.iap_status = "success";
       condition.receipt = {$in: [/^129/, /GPA./]};  
       db.collection('android_uc_iap').distinct("device_id", condition, function (err, docs) {
           callback(docs);
       });
};


// Calling it

getPayerIDs(db, function(theResult){
               console.log(dbname);
               console.log(theResult);
               payers = payers.concat(theResult);
               numberCollected++;
               if (numberCollected == 12) {  // async so need a way to know when it’s done
                   payers = unique(payers);
                   console.log(‘Print unique payers');
                   console.log(payers);
               }
});