Question

I’m working on an angular app and am running into a problem. I’m fairly new to JS and very new to asynch programming so I’m guessing I’m missing something obvious.

The gist of the problem is that I have a for loop which builds an array. I then need to join that array as soon as the for loop has completed it’s business. Normally this would be a no brainer but apparently in angular the for loop executes asynchronously. I need to force my array join to happen after the for loop exits.

if(!data.results[i].is_deleted) {
  var objectsOnCurrentPermission = new Array();
  if(data.results[i].objects) {
    for(var j = 0; j < data.results[i].objects.length; j++) {
      var currentObjectId = data.results[i].objects[j].object_id;
      var currentObjectName;
      var objectData = Object.get({id: currentObjectId}, function(objectData) {
        objectsOnCurrentPermission.push(objectData.name);
        console.log('in loop in get fn');
        console.log(objectsOnCurrentPermission);
      });
    }
    console.log('after loop');
    console.log(objectsOnCurrentPermission);
    var listOfObjectsOnCurrentPermission = objectsOnCurrentPermission.join(', ');
    console.log('str after assignment');
    console.log(listOfObjectsOnCurrentPermission);
    data.results[i]['objects_list'] = listOfObjectsOnCurrentPermission;
}

To my surprise, when I inspect the output I see (I added ‘<‘s for readability)

after loop permissions.js:246
>Array[1]
permissions.js:247
str after assignment permissions.js:249

permissions.js:250
in loop in fn permissions.js:242
>Array[1]

You can see that the after loop output executes first. From what I can tell, the first time it outputs Array[1] the array isn’t actually populated – chrome just fills it in after the fact. The the blank line after the line that says “str after assignment” is where I try to output of the join which clearly didn’t work. Then finally the code in the loop executes. As I mentioned I need to make sure that array join happens after the for loop has finished populating the array.

Answer 1

I ended up using caolan’s async library to manage my sync/async code needs. Specifically async.parallel allowed me to build the intermediate arrays and ensure they are complete before moving on. https://github.com/caolan/async