Thursday, December 19, 2013

CoffeeScript Application Development by Ian Young

I had the opportunity to read CoffeeScript Application Development by Ian Young recently and thought I would put together a book review.

The author does a nice job describing why parentheses are required for executing CoffeeScript no-argument functions. This is an idiom that I have seen many developers trip over when first coming to CoffeeScript. CoffeeScript preserves JavaScript’s view of functions as first-class citizens. Parentheses are optional except when necessary to avoid ambiguity.

The author gives some nice examples of loop comprehensions, one of the snazzier features of CoffeeScript. Loop comprehensions come from Python and they make for a more readable way to iterate a list and selectively act on list elements which meet a certain criteria. I’m always looking for more examples of loop comprehensions in CoffeeScript and this book has some nice examples.

The CoffeeScript switch statement is explained thoroughly. This is a handy flow-control statement that works really well in its incarnation in CoffeeScript. There are numerous examples in the book where different usage scenarios are demonstrated. Very handy and welcomed.

I found the author’s treatment of classes and inheritance in CoffeeScript to be a nice, gentle introduction. The examples that are given in the book work well and the explanations that accompany the examples are clear and concise. It would have been nice to get an explanation of the boilerplate code that CoffeeScript generates for you when defining a class, but I guess that’s considered part of the magic of CoffeeScript. It isn’t until the discussion on inheritance that the author starts to poke his head under the hood to investigate the generated JavaScript. The inheritance discussion is extremely valuable and a big plus for this book. If you get this book for anything, it’s for this discussion. CoffeeScript is doing a whole bunch of interesting stuff when creating classes and implementing inheritance, and this is one of the first times that I have seen the generated JavaScript described line by line.

In typical fashion, the author introduces the fat arrow syntax in a gentle manner, clearly explaining the reasoning for such a feature. The author then gives a very good explanation why you should not overuse the fat arrow syntax in your CoffeeScript (hint, it’s due to memory usage). He also includes a very succinct definition and example around memoization in CoffeeScript. This is a feature that I have not had much exposure to, so it was great to see it described and used in an example.

IcedCoffeeScript is introduced in the chapter on Going Asynchronous. I have not used IcedCoffeeScript, so that was an interesting exploration into an extension to CoffeeScript for managing asynchronous invocations. Looks interesting.

The topic of debugging CoffeeScript is broached. This is an interesting subject, as I have seen a few developers really get frustrated with the mapping of generated JavaScript back to the original CoffeeScript. Luckily the author introduces source maps, which does this work for us. The author shows us how to set this feature up in Firefox and Chrome developer tools. Your mileage will vary on this feature, but it is an interesting tool for easing the inertia of moving to CoffeeScript. This discussion comes with a lot of screenshots that help you understand how the source maps feature can be used in the developer tools.

Overall I really liked this book and it’s a worthy addition to my other documentation on CoffeeScript. Link to the book


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