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.

• slebetman: Is matchedArray[i].nearestmatch an array?
• Subburaj: @slebetman ys its an array..
• vp_arth: Are you looking for else statement?
• vp_arth: Outer for loop must be async too... async.times for example.

Answer 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.

• vp_arth: Also, you can return findById instead of else.

Answer 2

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
});