Christian Heilmann

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Archive for December, 2013

Teaching people to think about code instead of acing a test

Thursday, December 19th, 2013

One of my biggest bugbears with education, learning and teaching – especially online – is the focus we have on testing people by giving them multiple choice questions or having them fill out a very specific and rigidly defined test. This is a remnant from school education, where it is important to compare pupils and to also make it easy to measure the success rate and effectiveness of the teacher. Overly simplified, our school systems are designed to create new professors, not people who use the knowledge elsewhere. Ken Robinson covered this nicely in his TED talk How schools kill creativity and Salman Khan (founder of Khan Academy) ran with it in his TED talk as well.

The problem with rigid tests is that they can be gamed. I knew quite a few students and interviewees who learned information by heart, aced tests and came out not remembering a single thing let alone being able to apply the knowledge in a different scenario. The learned the what, but not the why.

calvin finds a loophole in a test

Job interviewers make the mistake of having a fixed set of questions and then compare different applicants by how they fared. This is not only boring for the interviewer, it also doesn’t tell you much about how the person you interview ticks. And in the end you want to work with that person, see them grow and apply their problem solving skills in various different scenarios. At Yahoo we had a great way of doing this – we gave people a code exercise that encompassed creating a small web site from a photoshop comp. We told them what the thing should do and then let them decide how to approach it. We looked at the result they sent us and if it worked nicely, we invited them to an interview where the first half hour or hour was them explaining to us why they approached solving the problem in a certain way, what their frustrations were, and how they cut corners and why. We learned a lot about the people that way, because programmers who can explain what they did are people who can code.

This is why I am very happy to see that some people are creative enough to approach teaching to code differently than others. There are quite a few new resources out there that teach coding by describing problems and asking the learner to write code that then gets validated in a worker thread (in the case of JavaScript). Code Combat for example is a beautiful product using that approach.

Yesterday I was super happy to see that Mozillian Brian Bondy who took in onto himself to create a series of videos explaining how to contribute to Firefox at added a series of small coding exercises to this endeavour.

Instead of telling you to “create variable a and assign the value foo to it as a string” the exercises on are task descriptions like

Create a new variable declaration and initialize it with a literal value in one statement.

This teaches you the lingo (you might have to look it up to understand the question but you now what a declaration is afterwards) and allows you to choose what you want to do. You creatively code instead of answering a question. There is a text editor embedded in the page that analyses what you do and if you manage to get a task done, ticks it off for you. All you do is code instead of following yet another “next lesson” button navigation.

Even better is that Brian released the framework that allows you to create tests like that. Under the hood it uses Acorn by Marijn Haverbeke in a web worker to analyse the code and test it against assertions you defined in a simple API.

var c = new Codec();
c.addAssertion("x = 3;");
c.addAssertion("x++", { blacklist: true, otherProps: "hi" });
c.parseSample("if (x) { x = 3; }", function(err) {
  console.log('whitelist hit? ' + c.assertions[0].hit);
  console.log('blacklist hit? ' + c.assertions[1].hit);

The codefirefox exercise module code is available on GitHub.

I am very excited about this and hope that some people will take this on. Brian is doing a great job with this and more is to come.

Zebra tables using nth-child and hidden rows?

Thursday, December 12th, 2013

lion dressed as zebra

Earlier today my colleague Anton Kovalyov who works on the Firefox JavaScript Profiler ran across an interesting problem: if you have a table in the page and you want to colour every odd row differently to make it easier to read (christened as “Zebra Tables” by David F. Miller on Alistapart in 2004) the great thing is that we have support for :nth-child in browsers these days. Without having to resort to JavaScript, you can stripe a table like this.

Now, if you add a class of “hidden” to a row (or set its CSS property of display to none), you visually hide the element, but you don’t remove it from the document. Thus, the striping is broken. Try it out by clicking the “remove row 3” button:

The solution Anton found other people to use is a repeating gradient background instead:

This works to a degree but seems just odd with the fixed size of line-height (what if one table row spans more than one line?).

Jens Grochtdreis offered a pure CSS solution that on the first glance seems to do the job using a mixture of nth-of-type, nth-child and the tilde selector.

This works, until you remove more than one row. Try it by clicking the button again. :(

In essence, the issue we are facing here is that hiding something doesn’t remove it from the DOM which can mess with many things – assistive technology, search engines and, yes, CSS counters.

The solution to the problem is not to hide the parts you want to get rid of but really, physically remove them from the document, thus forcing the browser to re-stripe the table. Stuart Langridge offered a clever solution to simply move the table rows you want to hide to the end of the table using appendChild() and hide them by storing their index (for later retrieval) in an expando:

[…]rows[i].dataset.idx=i;table.appendChild(rows[i]) and [data-idx] { display:none }

That way the original even/odd pairs will get reshuffled. My solution is similar, except I remove the rows completely and store them in a cache object instead:

This solution also takes advantage of the fact that the result of querySelectorAll is not a live list and thus can be used as a copy of the original table.

As with everything on the web, there are many solutions to the same problem and it is fun to try out different ways. I am sure there is a pure CSS solution. It would also be interesting to see how the different ways perform differently. With a huge dataset like the JS Profiler I’d be tempted to guess that using a full table instead of a table scrolling in a viewport with recycling of table rows might actually be a bottleneck. Time will tell.

An open talk proposal – Accidental Arrchivism

Sunday, December 8th, 2013

People who have seen me speak at one of the dozens of conferences I covered in the last year know that I am passionate about presenting and that I love covering topic from a different angle instead of doing a sales pitch or go through the motions of delivering a packaged talk over and over again.

For a few months now I have been pondering a quite different talk than the topics I normally cover – the open web, JavaScript and development – and I’d love to pitch this talk to the unknown here to find a conference it might fit. If you are organising a conference around digital distribution, tech journalism or publishing, I’d love to come around to deliver it. Probably a perfect setting would be a TEDx or Wired-like event. Without further ado, here is the pitch:

Accidental arrchivism

Gamer's guide screenshot

The subject of media and software piracy is covered in mainstream media with a lot of talk about greedy, unpleasant people who use their knowledge to steal information and make money with it. The image of the arrogant computer nerd as perfectly displayed in Jurassic Park. There is also no shortage of poster children that fit this bill and it is easy to bring up numbers that show how piracy is hurting a whole industry.

This kind of piracy, however, is just the tip of the iceberg when it comes to the whole subject matter. If you dig deeper you will find a complex structure of hierarchies, rules, quality control mechanisms and distribution formats in the piracy scene. These are in many cases superior to those of legal distributors and much more technologically and socially advanced.

In this talk Chris Heilmann will show the results of his research into the matter and show a more faceted view of piracy – one that publishers and distributors could learn from. He will also show positive – if accidental – results of piracy and explain which needs yet unfilled by legal release channels are covered and result in the success of the pirates – not all of them being about things becoming “free”. You can not kill piracy by making it illegal and applying scare tactics – its decentralised structure and its very nature of already being illegal makes that impossible. A lot of piracy happens based on convenience of access. If legal channels embraced and understood some of the ways pirates work and the history of piracy and offered a similar service, a lot of it would be rendered unnecessary.

If you are a conference organiser who’d be interested, my normal presentation rules apply:

  • I want this to be a keynote, or closing keynote, not a talk in a side track in front of 20 people
  • I want a good quality recording to be published after the event. So far I was most impressed with what Baconconf delivered on that front with the recording of my “Helping or Hurting” presentation.
  • I’d like to get my travel expenses back. If your event is in London, Stockholm or the valley, this could be zero as I keep staying in these places

Get in contact either via Twitter (@codepo8), Facebook (thechrisheilmann), LinkedIn, Google+ (+ChristianHeilmann) or email (catch-all email, the answer will come from another one).

If you are a fan of what I do right now and you’d be interested in seeing this talk, spread this pitch far and wide and give it to conference organisers. Thanks.