When making asynchronous HTTP requests from javascript, it can be very easy for code to descend into a tightly coupled mess of spaghetti as more and more requests are added.

8th April 2012 Phil Booth in Javascript

When making asynchronous HTTP requests from javascript, it can be very easy for code to descend into a tightly coupled mess of spaghetti as more and more requests are added.

jQuery has some good, under-appreciated functions that help you to apply patterns that keep the codebase clean. They're members of the jQuery `Deferred` object and the javascript playground has a short beginner-level tutorial, which is an easier introduction to using them than the official jQuery documentation.

You can read the tutorial here:

http://javascriptplayground.com/blog/2012/04/jquery-deferreds-tutorial

An introduction to jQuery Deferreds | Blog :: The JavaScript Playground

Prior to jQuery 1.5, Ajax requests could get a bit messy. You'd probably do something like this, if we were making a simple get request: $(function() { $.get( "content.txt", function(resp) { console.log("first code block"); console.log(resp); } ); }); But this gives you a potential issue - what happens if this fails?

Phil Booth

If you're not using jQuery but are interested in the subject of deferreds/futures/promises as a pattern for asynchronous programming in javascript, there's a library called Q that implements them:

https://github.com/kriskowal/q

Does anyone have other recommendations in this area?

8th April 2012

8th April 2012 Phil Booth in Javascript

An introduction to jQuery Deferreds | Blog :: The JavaScript Playground

Phil Booth

JavaScript Guy

London, GB