Go Premium for a chance to win a PS4. Enter to Win

x
?
Solved

How to check the value of a returned promise

Posted on 2016-09-21
2
Medium Priority
?
55 Views
Last Modified: 2016-10-10
HI,
I have the following html with promises and defered in script tag :
<!DOCTYPE html>
<html>
  <head>
    <title>Create Note</title>
    <meta name="viewport" content="width=device-width,initial-scale=1,maximum-scale=1">
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
    <style>
        body {
            background-color: linen;
        }
        h1 {
            color: maroon;
            margin-left: 40px;
        }
    </style>
   
  </head>
  <body>
  <div id="note">note</div>
  <button id="button">toggle</button>
</body>
 <script>
     $('#button').on('click', function(){
         $('#note').toggle();

     });
    function poll(fn, timeout, interval) {
    var dfd = $.Deferred();
    var endTime = Number(new Date()) + (timeout || 2000);
    interval = interval || 100;

    (function p() {
            // If the condition is met, we're done! 
            if(fn()) {
                dfd.resolve();
            }
            // If the condition isn't met but the timeout hasn't elapsed, go again
            else if (Number(new Date()) < endTime) {
                setTimeout(p, interval);
            }
            // Didn't match and too much time, reject!
            else {
                dfd.reject(new Error('timed out for ' + fn + ': ' + arguments));
            }
    })();
    console.log('finished');
    return dfd.promise;
}

// Usage:  ensure element is visible
promise = poll(function() {
  return document.getElementById('note').offsetWidth > 0;
}, 2000, 150);

    </script>
</html>

Open in new window


I have got the promise object but how do i check what value it has  or whether the defered object was resolve or rejected.... Also i see there is no values set to it.
Its only doing dfd.resolve and reject do these set some value in the promise ??

Thanks
0
Comment
Question by:Rohit Bajaj
2 Comments
 
LVL 60

Accepted Solution

by:
Julian Hansen earned 2000 total points (awarded by participants)
ID: 41808633
Take a look at this small sample
<script>
$(function() {
  var dfd = $.Deferred();
  setTimeout(function() {
    dfd.resolve(100);
  } , 5000);

  dfd.then(function(val) {
    console.log('Resolved with value : ' + val);
  });
});
</script>

Open in new window

In this code we create a promise.
We start a timeout to simulate an Async operation.
We attach a then handler to the promise to do something with the value when the promise resolves.
When our timeout happens we resolve the promise with a value - this value is passed to the then callback where we use the value.
0

Featured Post

Ask an Anonymous Question!

Don't feel intimidated by what you don't know. Ask your question anonymously. It's easy! Learn more and upgrade.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

How to build a simple, quick and effective accordion menu using just 15 lines of jQuery and 2 css classes
International Data Corporation (IDC) prognosticates that before the current the year gets over disbursing on IT framework products to be sent in cloud environs will be $37.1B.
The viewer will learn how to dynamically set the form action using jQuery.
The viewer will learn the basics of jQuery including how to code hide show and toggles. Reference your jQuery libraries: (CODE) Include your new external js/jQuery file: (CODE) Write your first lines of code to setup your site for jQuery…
Suggested Courses

886 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question