CODEWITHSUNDEEP
javascriptnode.jsreturnbreakasynccallback
Brian
Brian

Reputation: 310

Break out of a "for" loop within a callback function, in Node.js

Regarding the code below, my goal is to break out of FOR LOOP B and continue with FOR LOOP A, but within a callback function.

for(var a of arrA) {
    // ...
    // ...

    for(var b of arrB) {
        // ...
        // ...

        PartService.getPart(a.id, function(err, returnObj) {
            break;
        });
    }
}

Will this give me the results I want? If not, how can I achieve this?

EDIT 4/28/16 3:28 MST

Based on one of the answers and all the comments below, without changing the scope of the question, perhaps the best question at this point is "How do I implement a synchronous callback function in Node.js?". I am considering refactoring my code so to remove for loops, but I am still curious if I can still go in this direction using synchronous callback functions. I know that Underscore.js uses synchronous callback functions, but I do not know how to implement them.

Upvotes: 0

Views: 2767

Answers (2)

Jakub Rożek
Jakub Rożek

Reputation: 2130

You can try something like this, however it will work only when the callback is fired synchronously.

for(var a of arrA) {
  let shouldBreak = false;
  for(var b of arrB) {
    if (shouldBreak)
      break;
   // rest of code
     PartService.getPart(a.id, function(err, returnObj) { // when the callback is called immediately it will work, if it's called later, it's unlikely to work
       shouldBreak = true;
    });

Upvotes: 2

Sumeet Kumar Yadav
Sumeet Kumar Yadav

Reputation: 12945

This might not give you expected result . You can use events EventEmitter or async module .

Upvotes: 0

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