Part 9: Understanding JavaScript Async Promises

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Description

In this lesson, we backtrack and learn about the Async features in the WinJS Library. We cover the basics of processes and threads, how the Windows 8 execution model has changed, how apps have traditionally handled long running operations, and how Async Promises simplifies development and debugging of async operations.

 

Asynchronous programming in JavaScript

https://msdn.microsoft.com/en-us/library/windows/apps/hh700330.aspx

 

WinJS Promise Example

https://code.msdn.microsoft.com/windowsapps/Promise-e1571015

 

 

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The Discussion

  • User profile image
    mshaw

    Isn't promises callbacks under the cover?

  • User profile image
    BobTabor

    @mshaw: I don't claim to be the expert on this at all.  I have an "end user's" knowledge.  However, this article:

    http://dev.bennage.com/blog/2012/08/21/winjs-unpacking-promises/

    ... does a really nice explaining what the promise really is and how it relates to callbacks.

    "A promise is an object. It is not a function and it is not the value returned from the async operation. To get to the value, you need to call the then method on the promise object. You pass a callback function as an argument to then. The promise invokes the callback and passes the value you're interested in into the callback. Clear as mud, right?"

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