Part 9: Understanding JavaScript Async Promises

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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





The Discussion

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    Isn't promises callbacks under the cover?

  • User profile image

    @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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