Escape a "for" loop from within a callback function in Node.js

My objective with the code snippet below is to exit FOR LOOP B and continue with FOR LOOP A by utilizing a callback function.

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

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

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

Is this approach going to yield the desired results? If not, what alternative method should I employ?


UPDATE: 4/28/16 3:28 MST

  • The callback function operates asynchronously as confirmed

Considering the feedback from one of the responses and various comments provided below, sticking to the original context of my question, perhaps the revised inquiry at this stage ought to be "How can I integrate a synchronous callback function in Node.js?". Although I am contemplating restructuring my code to eliminate for loops, I am still interested in exploring the possibility of using synchronous callback functions. While I am aware that Underscore.js employs synchronous callback functions, the implementation process remains unknown to me.

Answer №1

Here is an example you can experiment with, but keep in mind that it will only function properly if the callback is triggered synchronously.

for(var x of arrayX) {
  let shouldStop = false;
  for(var y of arrayY) {
    if (shouldStop)
      break;
   // more code here
     ProductService.getProduct(x.id, function(error, result) { // when the callback executes immediately, it will work; if it's delayed, success is not guaranteed
       shouldStop = true;
    });

Answer №2

It's possible that the outcome may differ from your expectations. To address this, you could consider utilizing either the EventEmitter or async module.

Answer №3

Another approach could be to have the program run continuously without using a traditional for loop, thereby allowing it to operate asynchronously.

for (let x of myArray) {
    let _run = function(counter) {

        // Perform actions on another array
        
        Service.getData(id, function(error, result) {
            if (error) {
                throw error;
            }

            if (result.success) {
                // If successful, continue running the function
                _run(counter + 1);
            } else {
                // Exit the recursive loop
            }
        });
    };
    // Start the continuous operation
    _run(0);
}

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