node.js and promise

[Reza Razavipour]

I am a fairly new to javaScript and node.js both.

I am trying to wrap my head around promises and I am having a hard time. I am looking for a very simple tutorial/video on this topic and having little success.

Is there a reference that can be recommended? A before and after code snippet can be a good starting position.

Reza

[Gorgi Kosev]

Try http://spion.github.io/promise-nuggets - its not complete yet but the main concepts are covered

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[Angel Java Lopez]

I just found this link at es-discuss

http://flippinawesome.org/2013/10/14/a-simple-visual-model-for-promises/

[Jason Crawford]

Here are some good references:

http://blog.jcoglan.com/2011/03/11/promises-are-the-monad-of-asynchronous-programming/

http://domenic.me/2012/10/14/youre-missing-the-point-of-promises/

Enjoy,

Jason

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[Qihan Zhang]

Hi Reza,

I was just trying to wrap my head around how promises work yesterday and I highly recommend this article:

http://domenic.me/2012/10/14/youre-missing-the-point-of-promises/

I'm pretty new to node.js as well and found the explanation here very easy to understand.

Also, I would take a look at the documentation on https://github.com/kriskowal/q

Thanks,

[Mariusz Nowak]

Reza, check this before and after example: https://github.com/medikoo/deferred#plain-nodejs-callbacks-approach and once I tried explain promises to newcomers with following slides: http://www.medikoo.com/asynchronous-javascript/ it's nearly two years old, but still mostly up to date. Maybe that'll be helpful.

[Gary Katsevman]

There is also the Promises/A+ spec itself [http://promisesaplus.com/] which is fairly readable and can give more insight into promises.

Gary Katsevman
gkatsev.com

[Reza Razavipour]

we all of this I still can not figure out how to take an async function and change it from callback to a promise.

1. Do I have to declare a promise before I can call a 'then' on it? Every time I do not and call a then on an async function, I get a syntax error.

On Friday, October 18, 2013 3:11:47 PM UTC-7, Reza Razavipour wrote:

[Mariusz Nowak]

On 21 paź 2013, at 19:52, Reza Razavipour <reza.ra...@gmail.com> wrote:

we all of this I still can not figure out how to take an async function and change it from callback to a promise.

Many libraries provide it's own utils for that, just check their documentation:

https://github.com/kriskowal/q#adapting-node

https://github.com/medikoo/deferred#promisify---working-with-asynchronous-functions-as-we-know-them-from-nodejs

https://github.com/petkaantonov/bluebird/blob/master/API.md#promisepromisifyfunction-nodefunction--dynamic-receiver---function

1. Do I have to declare a promise before I can call a 'then' on it? Every time I do not and call a then on an async function, I get a syntax error.

On Friday, October 18, 2013 3:11:47 PM UTC-7, Reza Razavipour wrote:

I am a fairly new to javaScript and node.js both.

I am trying to wrap my head around promises and I am having a hard time. I am looking for a very simple tutorial/video on this topic and having little success.

Is there a reference that can be recommended? A before and after code snippet can be a good starting position.

Reza

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[Reza Razavipour]

Let us use an example:

var q = require('q');

    var myAsyncFunction = function(err, result) {

    if (err) 

    console.log("We got an error");

   

   

    console.log("Success");

    };

    myAsyncFunction().then(function () { console.log("promise is working"); });

myAsyncFunction().then(function () { console.log("it really worked"); });

                      ^

TypeError: Cannot call method 'then' of undefined

How do I turn myAsyncFunction into a promise?

[Mariusz Nowak]

var promisify = require('deferred').promisify;

var myAsyncFunctionPromiseVersion = promisify(myAsyncFunction);

myAsyncFunctionPromiseVersion().then(function () { console.log("it works!"); });

[Reza Razavipour]

wonderful... thank you.

and in q, what would that look like?

Regards,
Reza

[Reza Razavipour]

and what would that look like in q?

Is it Q.nfcall ?

On Friday, October 18, 2013 3:11:47 PM UTC-7, Reza Razavipour wrote: