Foreach callback when finish

Question

I want to execute a callback when foreach has finished, but it's not working properly.How can I do that?

var response = [];
myArray.forEach(function(data) {
    data.asyncFunction(function(result) {
         response.push(result);
    });
}, function() {
    console.log(response); // Not being called.
});

console.log(response); // (Empty) Executed before foreach finish.

*"// (Empty) Executed before foreach finish."* Incorrect assumption. The forEach is in fact complete. you are misdiagnosing the problem. Please provide more context to your question. — Kevin B, Jul 02 '15 at 19:49
@thefourtheye I edited because I'm using an asynchronous function inside my foreach. — Luciano Nascimento, Jul 02 '15 at 19:55

Anoop · Accepted Answer · 2015-07-02T20:04:43.360

12

Because forEach accept only one callback. Since you are calling asynchronous method inside forEach you need to check whether all asyn call completed

var response = [];
myArray.forEach(function(data, index) {
    data.asyncFunction(function(result) {
         response.push(result);
         if(response.length  === myArray.length) {
                 //foreach work done
         }
    });
});

edited Jul 02 '15 at 20:04

answered Jul 02 '15 at 19:47

Anoop

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I edited my question because I'm using an asynchronous function inside the foreach. Could you please take a look? Thanks. – Luciano Nascimento Jul 02 '15 at 19:56
2

if it is truly asynchronous, you can't trust that when the last index is called they are all done. better to compare myArray.length to response.length. – Kevin B Jul 02 '15 at 20:03
@Anoop Thank you guys, I got it! And sorry about the stupid question. – Luciano Nascimento Jul 02 '15 at 20:10
@LucianoNascimento it is not stupid question. it happen with every one – Anoop Jul 02 '15 at 20:12
You can use a simple integer variable and compare with **myArray.length** too (example: `if( itemsProcessed === myArray.length )` ) – JavierFuentes Apr 21 '18 at 18:16

PaulShovan · Answer 2 · 2015-07-02T20:05:06.483

4

Try this :

myArray.forEach(function(element, index, array){
  asynchronous(function(data){
       if (index === myArray.length - 1) {
           response.push(data);
           functionAfterForEach();
       }
  })
});

edited Jul 02 '15 at 20:05

answered Jul 02 '15 at 19:51

PaulShovan

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`myArray` is not changing... so whenever you call for it's length it will give the correct length @Kevin B – PaulShovan Jul 02 '15 at 20:08
1

the comment was of course to the original iteration of your answer. though, i think it still stands. if the last iteration of the loop finishes anything other than last, you'll call the callback too soon. – Kevin B Jul 02 '15 at 20:09
sorry @Kevin B it was a silly mistake for me – PaulShovan Jul 02 '15 at 20:09
sorry, see edits to comment. i have a bad habit of hitting enter in comments before i'm done. :) – Kevin B Jul 02 '15 at 20:11

Foreach callback when finish

2 Answers2