The Artima Developer Community
Sponsored Link

Agile Buzz Forum
Bliki: JavascriptPromise

0 replies on 1 page.

Welcome Guest
  Sign In

Go back to the topic listing  Back to Topic List Click to reply to this topic  Reply to this Topic Click to search messages in this forum  Search Forum Click for a threaded view of the topic  Threaded View   
Previous Topic   Next Topic
Flat View: This topic has 0 replies on 1 page
Martin Fowler

Posts: 1573
Nickname: mfowler
Registered: Nov, 2002

Martin Fowler is an author and loud mouth on software development
Bliki: JavascriptPromise Posted: Apr 22, 2013 9:00 AM
Reply to this message Reply

This post originated from an RSS feed registered with Agile Buzz by Martin Fowler.
Original Post: Bliki: JavascriptPromise
Feed Title: Martin Fowler's Bliki
Feed URL: http://martinfowler.com/feed.atom
Feed Description: A cross between a blog and wiki of my partly-formed ideas on software development
Latest Agile Buzz Posts
Latest Agile Buzz Posts by Martin Fowler
Latest Posts From Martin Fowler's Bliki

Advertisement

In Javascript, promises are objects which represent the pending result of an asynchronous operation. You can use these to schedule further activity after the asynchronous operation has completed by supplying a callback.

    aPromise = someAsyncOperation();
    aPromise.done(function() {
      // runs if all went well
    });
    aPromise.fail(function() {
      // runs if something went wrong
    });
    aPromise.always(function() {
      // runs either way
    }); 

As well as providing a clear interface to schedule activity with asynchronous tasks, they also compose.

      composedPromise = $.when(anAsyncFunction(), anotherAsyncFunction());
    

In this form (using jQuery promises) the composed promise will run its done handlers when all the passed promises succeed and its fail handlers if any of them fail.

There are various forms of promises in javascript, annoyingly they have subtly different APIs and vocabularies. Probably the most used is jQuery's Deferred Object.

You also hear these concepts described as futures and deferreds. These concepts appear in many languages, not just javascript, often with concurrency in mind as much as asynchrony.

For more information I suggest getting a copy of Trevor Burnham's Async JavaScript. If you want a web article, I found Burnham has a short but useful article summarizing them.

Read: Bliki: JavascriptPromise

Topic: The Paradigm of Project Management Tools Previous Topic   Next Topic Topic: User Stories : PMI-ACP Agile Certification

Sponsored Links



Google
  Web Artima.com   

Copyright © 1996-2019 Artima, Inc. All Rights Reserved. - Privacy Policy - Terms of Use