Make asynchronous call inside loop until a value is found

Question

I'm trying to do several calls inside a loop to an asynchronous API until the value that I want (true in this case) is returned. The issue is that I don't want to keep looping after that value is found and I don't want to execute the lines after the loop without the value returned from it...but so far I can't get that working. I think I'm doing something wrong here, but "I can't get the whole picture".

function isSelected(element, callback) {
  // This is a little bit confusing for me...can I just get the value from
  // getDataAsync without using isSelected function?
  Office.select(element).getDataAsync(function (asyncResult) {
    var result = true;

    // some logic here that may change 'result'
    callback(result);
  });
}

function delete(elements) {
  var index = -1;

  for (var i = 0, (i < elements.length) && (index < 0); i++) {
    isSelected(elements[i], function(result) {
      if (result) { index = i; }; // ...and I don't want to keep "looping"
    });
  }
  // I want to execute these lines after the for-loop is done
  // ...do something with the "correct" index value
}

Answer 1

Have you tried Kriskowal's Q? There's a nice function called Q#allSettled:

Q.allSettled(promises)
.then(function (results) {
    results.forEach(function (result) {
        if (result.state === "fulfilled") {
            var value = result.value;
        } else {
            var reason = result.reason;
        }
    });
});

So basically this is how it would work in your case:

var promises = [];

for(/* conditions */) {
  promises.push(/* async call which returns a promise */);
}

Q.allSettled(promises).then(function(results) {
    results.forEach(function (result) {
        var value;

        if (result.state === "fulfilled") {
            value = result.value;

            // do something with "value"
        }
    });
});

allSettled just makes sure the then will be executed regardless of whether or not the promise was successful or not, and you can check the value of the object you retrieve from your async call.