node.js async for loop

Question

My Scenario:

Inside a forEach loop i executed a function with callback as like below:

var rows = [];
rows.forEach(function(elem, i){
///done some stuff

     client.search(query).then(function(facResult){
     //done some stuff         
     });    
});

My problem is for first iteration the "client.search(query)" is executed before finishing this stuff the second iteration is started because client.search(query) is executed with callback. I have to push first all result into an array.

So before i am getting first result the second is appended, sometimes i am not getting even the first result.

What i have to do to execute the for loop in order. I searched a lot , some suggestions is to use timedelay, but i don't need that. Help me to solve this. Thanks in advance.

You can use async library. Look at this post: http://stackoverflow.com/questions/9644197/sequential-execution-in-node-js — Aviv Shaked, Feb 11 '15 at 05:44

score 0 · Answer 1 · edited May 23 '17 at 12:12

0

You are running into race-condition issues because of using 'forEach'. Instead of getting all the rows into 'rows', use a 'cursor' instead.

You can see the following answer for implementation which is similar to your use-case : https://stackoverflow.com/a/18119789/802651

edited May 23 '17 at 12:12

Community

1
1

answered Feb 11 '15 at 05:34

Adarsh Konchady

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its not a mongodb connection rows. Actually its just an array.. see my editd post.. – Subburaj Feb 11 '15 at 05:36
Could you create a fiddle for this then? – Adarsh Konchady Feb 11 '15 at 05:43

score 0 · Answer 2 · answered Feb 11 '15 at 06:40

I used async library for this as like below:

async.forEach(myVar.rows, function (elem, next){ 

    client.search(query).then(function(facResult){
     //done some stuff      
      if(--myVar.rows.length == 0){
          loop finishes //done some stuff
      }

     });  

});

node.js async for loop

2 Answers2