Update: September 7, 2012
I misunderstood how browser load external JavaScript files when that load itself comes from embedded script. Ben Ward explained it to me and referenced this handy article, Thinking Async.
The gist of the article is that using JavaScript to write in a call to a JavaScript file causes the browser to load the external script asynchronously.
While it may be like wearing suspenders with a belt, I'm still going to leave my async edits in my Twitter embedded timeline calls.
Original Entry
Yesterday Twitter announced its new embedded timeline feature for web sites. The gist is that you drop a block of code on your site and users will see the timeline for the selected account as if they were viewing it on Twitter.com — embedded media, expanded links, etc.
This is a new feature and is likely to change, even if the how-to Twitter post isn't too clear on that. I say that it will change because of language in the developer documentation like No other customization options are available at this time,
as well as the slew of requests for more type styling options (among other customization requests) on the Twitter Embedded Timelines Questions page(s).
There are also known bugs. If your domain has a hyphen in it, then this won't work. If you are using Opera Mobile, Android 2 or 3 default browser, or an iPad, then the swipe-to-scroll gesture doesn't work (I already reported that one).
Another issue that Twitter may not consider a bug is how the script to embed the timeline is loaded. Currently if you have an embedded tweet or the old embedded timeline on your page and Twitter is down (fail-whale down), then your web page will take quite a while to render. This is a function of how browsers load JavaScript. The browser won't finish rendering the page until it has loaded all the JavaScript or given up (a timeout, which can take minutes).
While there are JavaScript functions that can mitigate this, those don't come into play until the script has downloaded. Instead, HTML5 has a couple attributes for the script element that apply here — async and defer. Essentially these tell the browser it can render the page before the script is downloaded. Since Twitter content is often just add-on content for your existing page, this is the right approach.
Instead of spending a thousand words explaining how this attribute works, I refer you to the WHATWG specification using an embedded tweet where I manually insert the async attribute:
If you use JavaScript and don't know about async/defer HTML5 attributes, you should read up and use: whatwg.org/specs/web-apps…
— Adrian Roselli (@aardrian) September 6, 2012
The new embedded timeline feature doesn't make it quite that easy. Twitter gives you code to drop on your page that has no script element into which you can casually paste async. The script element is generated by JavaScript, which looks like this:
<a class="twitter-timeline" href="https://twitter.com/aardrian" data-widget-id="243755160277487616">Tweets by @aardrian</a>
<script>!function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs");</script>
Many of the people who may drop Twitter timelines into their web site are not JavaScript coders. So I whipped up a quick modification you can make to that pre-generated script that will drop the async attribute where it needs to go:
<a class="twitter-timeline" href="https://twitter.com/aardrian" data-widget-id="243755160277487616">Tweets by @aardrian</a>
<script>!function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.async=true;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs");</script>
The js.async=true; tells the Twitter function to drop an async into its script reference when it gets created. The generated chunk of code will look like this:
<script src="//platform.twitter.com/widgets.js" async="" id="twitter-wjs">
Now if Twitter goes down again (which it will) your page won't hang as a result.
I have also asked Twitter to consider including async in its standard copy-and-paste code.
I have eight (8!) examples of this in play on my Buffalo food truck page, where I have embedded the timelines of the current crop of food trucks in the area so I can check them all at once while aimlessly wandering the streets in a hunger stupor.
If you have a better solution, I am all ears. Please drop it in the comments with any other feedback.
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