How To Break A For Loop Inside An Asynchronous Callback Function

Question

I am trying to break a nested for loop inside a asynchronous call back but unable to do so:

function asyncCall(id, OnComplete) {
    // id..
    context.executeQueryAsync(OnSuccess, OnFailure);

    function OnSuccess(sender, args) {
        OnComplete(userInGroup);
    }

    function OnFailure(sender, args) {
        console.error("Doesn't Exist!")
    }
}

function callApi() {
    //response from intial call
    for (var key in response) {
        var data = response[key];
        (function (innerData) {
            if (innerData) {
                renderHTML(innerData);
            }
        })(data);
    }
}

function renderHTML(data) {
    for (var key in data) {
        var index = data[key];
        (function (innerData, id) {
            asyncCall(id, function (isFound) {
                if (isFound)
                    break; //break loop
            });
        })(data, index);
    }
}

callApi();

I want to break the loop if the value of the property isFound is true in its response and want to achieve this in ES5 only or any work around like synchronous call might help.

You can't with the structure you show unless you make the asyc calls synchronous. As shown, the entire loop will probably have fully ran before the first asyc call resolves. — Shilly
– Shilly, Commented Nov 12, 2018 at 15:33
This looks like Javascript breaking a for loop inside a callback function — Heretic Monkey
– Heretic Monkey, Commented Nov 12, 2018 at 17:22
@Shilly thanks for the knowledge, how can i call this asynchronous method synchronously then? — Asad Shah
– Asad Shah, Commented Nov 13, 2018 at 7:09
@AsadShah Instead of caliing asyncCall inside a loop, wait for the response to arrive and then call the next one. But depending on what executeQueryAsync does, you might be able to leave it async. Need more information for that thoguh. — Shilly
– Shilly, Commented Nov 13, 2018 at 9:22
@Shilly executeQueryAsync takes id as parameter and fetches data from the server and returns boolean if the user exists in a group or not but i have to leave it async as it is the function of third party library. calling function asyncCall sequentially will help but don't know exactly how to call it sequentially. — Asad Shah
– Asad Shah, Commented Nov 13, 2018 at 10:40

Quentin · Accepted Answer · 2018-11-12 15:33:14Z

0

You can't.

The loop will have finished before the break gets reached.

The only way to do this would be to run each invocation of asyncCall in series instead of in parallel. (e.g. by calling the next one from the callback function passed to the previous one).

answered Nov 12, 2018 at 15:33

Quentin

949k136 gold badges1.3k silver badges1.4k bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Asad Shah Over a year ago

"The only way to do this would be to run each invocation of asyncCall in series instead of in parallel". Can you show it with the help of some example ?

jacksbox · Accepted Answer · 2018-11-12 15:34:47Z

0

As Quentin said, you can't.

But if you want to prevent further callbacks from happening, you could set a variable which prevents the callbacks to happen.

let isFound = false;

function asyncCall(id, OnComplete) {
  // id..
  context.executeQueryAsync(OnSuccess, OnFailure);

  function OnSuccess(sender, args) {
      if(isFound) return;
      isFound = true;
      OnComplete(userInGroup);
  }

  function OnFailure(sender, args) {
      console.error("Doesn't Exist!")
  }
}

answered Nov 12, 2018 at 15:34

jacksbox

9291 gold badge13 silver badges26 bronze badges

2 Comments

Asad Shah Over a year ago

At the moment i am doing exactly what you said, but don't want unnecessary calls to hit.

jacksbox Over a year ago

hit the onSuccess function? or the api?

Collectives™ on Stack Overflow

How To Break A For Loop Inside An Asynchronous Callback Function

2 Answers 2

1 Comment

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related