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Uploaded byjasonsich
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Gr Node Dev Promises Presentation

A promise represents the result of an asynchronous operation. It provides methods to handle callbacks from async operations. Using promises allows returning results from functions instead of injecting callbacks into low-level code, which provides more control, flexibility, and readable code. Promises get resolved once the async operation occurs and can be fulfilled successfully or rejected. Common promise methods include then(), catch(), and done().

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Promises Never gonna give you up Never gonna let you down Never gonna tell a lie and hurt you Created by Jason Sich / @jasich
What is a promise? A promise is an object that represents the result of an asychronous operation, which may or may not have happened. They provide methods for control flow to handle the callback of an asynchronous operation.
Why would you want that? So that you can start returning data from your functions instead of injecting high-level code into low-level code (callbacks).
Why would you want that? (cont...) Consider how much more powerful it is to return results to high level code, rather than injecting functionality into low-level code. You get more... Control Flexibility Better Code Readability
Terminology Resolution Promises only get resolved once resolved - Async operation has occurred unresolved - Async operation has NOT occurred YET Fulfillment fulfilled - When a promise is resolved successfully rejected - When a promise is NOT resolved successfully Other thenable - You can chain any function that returns a value after the initial then
How do I promise? Well they aren't quite native in node yet (in beta). But there are many npm packages that allow you to use them. q promise node-promise When looking at promise libraries try to get something that conforms to the Promises/A+ spec
Control Flow Promises provide methods for control flow. then() catch() done() others names/availability depend on spec implementation
Examples https://github.com/jasich/promisesPresentation/tree/master/src
The End Created by Jason Sich @jasich on Twitter jasich on GitHub