Flows of energy

by Marijn Haverbeke (license)

Review: If Hemingway Wrote JavaScript

Monday, September 8, 2014 javascript books

Four out of five stars. Would read again. ★★★★☆

When Angus Croll first told me that he was working on a book that solves simple programming exercises in the style of various famous literary authors, I couldn't help but suspect that such a book would be completely pointless, and he wouldn't sell ten copies. After reading the result of his efforts, I still firmly stand by the latter prediction, but I have to admit that I actually enjoyed this book.

If Hemingway Wrote JavaScript is a slim, prettily typeset book that is divided into five programming exercises, and has five authors solve each of the exercises. It accompanies each solution with a brief description of the author's background and style, and a detailed walk-through of the code.

Wild experiments are what moves a genre forward. And this is a format of programming book that's certainly never been tried before.

The exercises are very simple—think Fibonacci and factorials. But some of the solutions are absolutely charming. Here's Jorge Luis Borges finding prime numbers, transforming the problem into a story about long-legged monsters climbing a set of stairs:

// They speak (I know) of finials, newels and balustrades
// of hidden spandrels and eternally clambering, broad-gaited beasts...

var monstersAscendingAStaircase = function(numberOfSteps) {
  var stairs = []; stepsUntrodden = [];
  var largestGait = Math.sqrt(numberOfSteps);

  // A succession of creatures mount the stairs;
  // each creature's stride exceeds that of its predecessor.
  for (var i = 2; i <= largestGait; i++) {
    if (!stairs[i]) {
      for (var j = i * i; j <= numberOfSteps; j += i) {
        stairs[j] = 'stomp';

  // Long-limbed monsters won't tread on prime-numbered stairs.
  for (var i = 2; i <= numberOfSteps; i++) {
    if (!stairs[i]) {

  // Here, then, is our answer.
  return stepsUntrodden;

You can tell that the author spent a lot of time on these snippets, polishing the style and adding intricacies—like the fact that the inner loop starts at i * i in the code above. Which it can, but it takes a second take to figure out why. If you approach these as you would normally approach code, they are just misguided blobs of confusion and weird variable names. But if read as stories and logic puzzles, they are very interesting. Several of the solutions initialled looked like they could not possibly work. Yet when I tried them out, they all worked—except for the intentionally broken solution at the end of the book.

Another thread that runs through the book is a critique of the limiting, constrained coding style advocated by tools like JSLint. Angus argues that coding in a uniform subset of a flexible language like JavaScript robs us of a lot of expressivity and artistic freedom.

This is a point I mostly agree with. Though the of literary JavaScript explored in this book doesn't seem to hold much promise for production code, it can take a place in our cultural background as a useful reminder of what you can do with this language.

All in all, I had a good time with this book. But then, I should, because I am the precise target audience: a JavaScript programming literature nerd with a taste for bizarre coding styles. In the unlikely event that this also describes you, give this book a try. (If there's ten of us, we might even disprove my prediction about the book's sales.)

As a bonus, here's my attempt to have Hunter S. Thompson compute prime numbers.

// It's four in the morning, and I'm desperately late with this
// goddamn assignment. I'm going to go ahead and assume you'll use
// this in your book, and I expect a fat cheque in the return mail.

function indivisibleFreaks(limit) {
  var freaks = []

  // Line them all up...
  offTheHook: for (var number = 2; number <= limit; number++) {
    // ...and drop the screwups with a .44 Magnum.
    for (var aim = 0; aim < freaks.length; aim++)
      if (number % freaks[aim] == 0) continue offTheHook;

  // What you bastards want with these poor guys, I can only imagine.
  return freaks;