Running JavaScript... With Sneakers!

Code-review time. I haven't written significant JavaScript in forevs, but I hit upon a use case well suited to it, had a blast coding it up, and am confident that I'll be completely mystified by it three months from now. That is, unless we refactor it for maintainability (this is where you come in).

I'll explain the use case. The Couch-to-5K running plan is an excellent exercise regimen for learning to run. I followed it to successfully transform myself from sedentary software developer to 5K finisher. The runners among you know that five kilometers is a beginner-level distance; the sedentary software developers may find it as daunting as I once did. You train in intervals, alternating walking and running, gradually shifting the ratios to more running in successive workouts. If you can walk a moderate distance, following the program is totally doable (or modify it for easy walking/fast walking, if you're not up for jogging). Definitely check it out.

The thing is, timing the intervals—especially at the beginning, where you're alternating a minute of running with 90 seconds of walking—needs a complex timing device (a fancy runners watch), and if you're using a treadmill, it is really annoying to your fellow gym users, as your watch is beeping every minute or two. Or, well, maybe gym people don't care, but it's really annoying to me, since the dang thing is on my own wrist. For running indoors, I want a C25K timer that is tactile or visual. I've been thinking about an Arduino-powered timer that reads from a dip switch to determine which workout you're running and signals the changes with a vibration motor (like in a cell phone). Thinking, and not so much doing. Finally one Sunday I forced myself to focus on the problem: what do you have, with a visual display, that is really small and runs code?

My Nokia N810 internet tablet has a web browser that runs JavaScript, can open html files stored locally, and can do this while also playing a podcast. Win!

Here's what you can't do with JavaScript, though: Thread.Sleep(walkInterval). Instead, you use setTimeout() to say "execute this function after this interval," asynchronously. That's the part that currently works but I daren't touch it. In other words, that's the part that needs your code review advice. Remember that the intended scenario is to rest the tablet on the treadmill's magazine lip, so the app flashes the background of the page to catch my eye when I'm not looking directly at it. It's high-contrast because it isn't meant to be watched, just kept at hand, in my periphery.

If you choose to use the app (in addition to reviewing it), please only use it on a treadmill. Stay safe; don't try to wrangle something you need to look at while you're on the trail.

The Running Timer code is on github. A representative sample is below. How would you make it better?

var exercise = function(setup) {
 var workout = getWorkout(setup.week,;
 doExercise(workout, 0);

var cooldown = function() {
 walk('Cool Down');
 window.setTimeout(function() { transition(function() { walk('Done!'); })}, 

var doExercise = function(workout, i) {
 if (i === workout.length - 1) {
  window.setTimeout(function() { transition(cooldown) }, 
 } else {
  window.setTimeout(function() { transition(function() { doExercise(workout, i + 1); })}, 

var getWorkout = function(week, day) {
 return eval('C25K.W' + week + 'D' + day);

var transition = function(callback) {
 var indicatorDiv = $('.runCountdown');
 var body = $(document.body);
 transitionBlink(6, indicatorDiv, body, callback);