mySociety

We had a complaint that FixMyStreet maps weren’t displaying on someone’s computer. We hadn’t had any other complaints, and we quickly narrowed it down to the fact that the person was on the internet using a tethered T-Mobile phone.

T-Mobile (and Orange, and quite possibly others) are injecting JavaScript and altering content served over their networks. Their reason for doing this, according to their websites (T-Mobile, Orange), is to compress images and video sent to your browser, so as to speed up your browsing. Seeing it in action, they also inline some CSS and JavaScript, though not all, and remove comments from external files.

However, their implementation breaks things. In this particular instance, the T-Mobile JavaScript comment stripper appears to be searching for “/*” and “*/” and removing everything inbetween. This might work in most cases; however in the jQuery library, we find a string containing “*/*”, and later down the file, another string containing “*/*”. T-Mobile remove everything between the things it thinks are comment markers, even though they’re actually contained within strings, causing the jQuery library to be invalid JavaScript and stopping anything using jQuery from running.

Their decision to inline lots of the CSS also seems a bit odd – sure, on a mobile this might be quicker, but even ignoring tethering nowadays plenty of mobiles have caches too and having the CSS download once and be cached would seem better than adding weight to every page download. But I’m sure they’ve studied their decision there, and it doesn’t make any difference to the actual browsing, as opposed to the comment removal.

To turn off this feature on your mobile phone or broadband, visit accelerator.t-mobile.co.uk or accelerator.orange.co.uk on your connection and pick the relevant option – if anyone knows of similar on other networks, do leave updates in the comments.

From a FixMyStreet point of view – whilst FixMyStreet functions just fine without JavaScript, I had made the (perhaps incorrect) decision to put the map inside a <noscript> element, to prevent a flash of map-oddity as the JavaScript map overlaid the non-JS one. However, this meant in this circumstance the map did not work, as JavaScript was enabled, but jQuery was unable to be loaded. I haven’t decided whether to change this behaviour yet; obviously it would help people in this situation as the map would still display and function as it does for all those without JavaScript, but for those with JavaScript it does look a bit jarring as the page loads. Any suggestions on a better approach welcome