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Part 9: Understanding JavaScript Async Promises

12 minutes, 11 seconds


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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



WinJS Promise Example





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  • mshawmshaw

    Isn't promises callbacks under the cover?

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


    ... 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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