Async flow in node.js

Question

In my node.js application i want to make my flow synchronous. I faced this kind of issues previously, i solved it. But now i am struggling now in this situation.

for(var k=nearestMatchLength;k--;) {
    async.forEach(matchedArray[i].nearestmatch, function(elem,Callback){
       if(condition){
          app.models.Schedule.findById(elem.Id, function(err, res){
             for(){
             };----> for loop 
             Callback(); 
          });
       }
        Callback();
    });
}

In the above code if(condition) satisfied then the findById(which is async) is called and the Callback(); after that is called before its executes.

My flow should be if it entered into if condition the fetching should be done and then only the next loop should rotate.

Please share your ideas. thanks in advance.

Outer for loop must be async too... async.times for example. — vp_arth
– vp_arth, Commented Aug 26, 2016 at 5:19

Ruchan · Accepted Answer · 2016-08-26 05:27:57Z

1

for(var k=nearestMatchLength;k--;) {
    async.forEach(matchedArray[i].nearestmatch, function(elem,Callback){
       if(condition){
          app.models.Schedule.findById(elem.Id, function(err, res){
             for(){
             };----> for loop 
             Callback(); 
          });
       }
       else{
        Callback();
       }
    });
}

the else is added there because your app.models.Schedule.findById has a callback function(err, res) which lets the bottom Callback() be called before even getting to the function(err,res) part.

so here is an example

console.log('A');
setTimeout(function(){
   console.log('B');
  },0);
console.log('C');

Whats the order of the letters printed here??

Its A, C then B

The example here is of setTimeout but it can be anyother function with a callback implemented.

answered Aug 26, 2016 at 5:27

Ruchan

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1 Comment

vp_arth Over a year ago

Also, you can return findById instead of else.

Medet Tleukabiluly · Accepted Answer · 2016-08-26 05:58:44Z

There is no async.forEach, and you can get rid of for loop

//async.times - execute fn number of times
async.times(nearestMatchLength, function(i, next){
    async.each(matchedArray[i].nearestmatch, function(elem, callback){
       if(true){
          app.models.Schedule.findById(elem.Id, function(err, result){
             //do something async
             //for example it's a new for loop
             async.each([1,2,3], function(number, cb) {
                //do some work
                result.number = number;
                //call cb to reach next iteration
                cb();
             }, function() {
                //all elements from [1,2,3] complete
                //do some async again and call next to complete
                //async.times execution
                result.save(next);
             });
          });
       } else {
          next(null);
       }
    });
}, function(err, done) {
    //complete
});

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