JavaScript promises on Cobalt

Ryan Morlok
Ryan Morlok ✭
in TR Internal
What [implementation of the promises pattern][1] are we using on Cobalt? I assume it might be different between ADC and "Classic Cobalt JavaScript", so information on both would be appreciated. [1]:
http://blog.parse.com/2013/01/29/whats-so-great-about-javascript-promises/
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  • James Greene
    James Greene
    Answer ✓
    In the "Cobalt Static Content" world (i.e. not ADC, not Viper), I only found a relatively short list of promise usage and it's all using jQuery: `$.Deferred`, `$.when`, `$.ajax(...).done`, etc. Usage is notably higher among the newer feature teams than the module teams. jQuery's promises implementation is useful but also not Promises/A+ compliant, so it may not be what you're seeking either. If you want to get more into Promises, I'd recommend one of the following based on personal experience and/or research: 1. [when.js](
    https://github.com/cujojs/when) 2. [Q](
    https://github.com/kriskowal/q) 3. [RSVP.js](
    https://github.com/tildeio/rsvp.js) Note that both when.js and Q can _consume_ jQuery promises using their respective `when` methods. After using Q for promises on Node.js for a number of projects, I actually ended up dropping promises in favor of simplified continuation passing with [async.js](
    https://github.com/caolan/async), partially because of the convenience of having _less_ abstraction to try to keep straight but mostly because of its advanced patterns like [`async.parallelLimit`](
    https://github.com/caolan/async#parallellimittasks-limit-callback) (check out their docs!). Async.js fits especially well into the Node.js world given Node's defacto continuation pattern APIs but it can also be used in the browser.

Answers

  • Andrew Gerber
    Andrew Gerber
    Considering that jQuery is the main low level framework in use throughout Cobalt, jQuery's Deferred is the implementation that is/should be used.
  • Ioannis Mavroukakis
    Ioannis Mavroukakis
    That's very interesting. I've found that CPS in Node has frequently led me to callback hell, with deeply nested blocks that are harder to read. Once replaced with Q the code (and the intention) becomes instantly more readable. especially if you take advantage of things like promiseAll(). There's a good article on why coroutines won't work for the Web here
    http://calculist.org/blog/2011/12/14/why-coroutines-wont-work-on-the-web/

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