CODEWITHSUNDEEP
javascriptjquerypromisejquery-deferreddeferred
asparism
asparism

Reputation: 614

jQuery Promise doesn't trigger .then() or .done()

I'm trying to use a promise to make sure a certain function doesn't fire until another function has returned. I've looked at a lot of examples, others' problems etc., and as far as I can tell my syntax is correct, but my .then(function()) won't run, so I must be missing something.

function previewMaster () {

var dfd = $.Deferred(); 

  function prevAndTest() {
    return true;
  }

  var doneYet = false;

  var intvl = setInterval(function() {
    if (doneYet === false) {
      doneYet = prevAndTest();
      //reassign doneYet until true
    } else {
      clearInterval(intvl);
      dfd.resolve;
     return dfd.promise();
    }
  }, 1000);
}

neither .then() nor .done() work here:

var promise = previewMaster();
  promise.then(function() {
    alert("finished");
  });

Upvotes: 0

Views: 880

Answers (1)

Andrea
Andrea

Reputation: 3440

You solution does not work because the method previewMaster is not returning the promise:

function previewMaster () {
    ...
    return dfd.promise();
}

and because you need to call the resolve function when you want to resolve the promise:

dfd.resolve();

See the complete example here:

function previewMaster () {

    var dfd = $.Deferred(); 

    function prevAndTest() {
        return true;
    }

    var doneYet = false;

    var intvl = setInterval(function() {
        if (doneYet === false) {
        doneYet = prevAndTest();
        //reassign doneYet until true
        } else {
        clearInterval(intvl);
        dfd.resolve(); // <- resolve method must be called to resolve the promise.
        // return dfd.promise(); // <- Do not return the promise here
        }
    }, 1000);
    return dfd.promise(); // <- Return the promise here
}

Upvotes: 2

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