Some of My Dev8D Tinkerings – Yahoo Pipes Quick Start Guide, Cross-Domain JSON with JQuery and Council Committee Treemaps from OpenlyLocal

One of the goals I set myself for this year’s Dev8D was to get round to actually using some of the things I’ve been meaning to try out for ages, particularly Google App Store and JQuery, and also to have a push on some of the many languishing “projects” I’ve started over the last year, tidying up the code, making the UIs a little more presentable, and so on…

Things never turn out that way, of course. Instead, I did a couple of presentations, only one of which I was aware of beforehand!;-) a chance remark highlighting me to the fact I was down to do a lightning talk yesterday…

I did start looking at JQuery, though, and did manage to revisit the Treemapping Council Committees Using OpenlyLocal Data idea I’d done a static proof of concept for some time ago…

On the JQuery front, I quickly picked up how easy it is to grab JSON feeds into a web page if you have access to JSON-P (that is, the ability to attach a callback function to a JSON URL so you can call a function in the web page with the object as soon as it loads), but I also ran into a couple of issues. Firstly, if I want to load more than one JSON feed into a page, and then run foo(json1, json2, json3, json4, json5), how do I do it? That is, how do I do a “meta-callback” that fires when all the separate JSON calls have loaded content into the page. (Hmm – I just got a payoff from writing this para and then looking at it – it strikes me I could do a daisy chain – use the callback from the first JSON call to call the second JSON object, use the callback from that to call the third, and so on; but that’s not very elegant…?) And secondly, how do I get a JSON object into a page if there is no callback function available (i.e. no JSON-P support)?

I’m still stuck on the first issue (other than the daisy chain/bucket brigade hack), but I found a workaround for the second – use a Yahoo pipe as a JSON-P proxy. I’ll be writing more about this in a later post, but in the meantime, I popped a code snippet up on github.

On the Openlylocal/council treemap front, I’d grabbed some sample JSON files from the Openlylocal site as I left Dev8D last night for the train home, and managed to hack the resulting objects into a state that could be used to generate the treemap from them.

A couple of hours fighting with getting the Openlylocal JSON into the page (solved as shown above with the Pipes hack) and I now have a live demo – e.g. http://ouseful.open.ac.uk/test/ccl/index-dyn.php?id=111. The id is the openlylocal identifier used to identify a particular council on the Openlylocal site.

If you’re visiting Openlylocal council pages, the following bookmarklet will (sometimes*;-) display the corresponding council committee treemap:

javascript:var s=window.location.href;s=s.replace(/.*=/,””);window.location.href=”http://ouseful.open.ac.uk/test/ccl/index-dyn.php?id=”+s;

(It works for pages with URLs that end =NNN;-)
Council committee treemap

The code is still a bit tatty, and I need to tidy up the UI, (and maybe also update to a newer JIT visualisation library), so whilst the URI shown above will persist, I’ll be posting an updated version to somewhere else (along with a longer post about how it all works) when I get round to making the next set of tweaks… Hopefully, this will be before Dev8D next year!;-)

PS I also had a huge win in discovering a javascript function that works at least on Firefox: .toSource(). Apply it to a javascript object (e.g. myobj.toSource() and then if you do things like alert(myobj.toSource()) you can get a quick preview of the contents of that object without having to resort to a debugger or developer plugin tool:-)

PPS can you tell my debugging expertise is limited to: alert(“here”); all over the place ;-) Heh heh…

Author: Tony Hirst

I'm a Senior Lecturer at The Open University, with an interest in #opendata policy and practice, as well as general web tinkering...

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