In JavaScript, there is a beautiful, elegant, highly expressive language that is buried under a steaming pile of good intentions and blunders. The best nature of JavaScript is so effectively hidden that for many years the prevailing opinion of JS was that it was an unsightly, incompetent toy.

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I disliked JavaScript until I read some of Douglas Crockford’s articles arguing that it is the world’s most misunderstood programming language. I pieced together a vision of a nice language burdened by misfeatures and poor implementations. In JavaScript: The Good Parts, Crockford fully realizes that vision in a dense, enjoyable book.

If you find yourself writing in JavaScript and not enjoying it, you need to stop and read this book. (Or even if you’ve just wondered why Steve Yegge obliquely goes on about it.) The book feels a bit like Kernighan and Ritchie in that it tersely defines the language and lets the reader work through the implications. I especially appreciate that Crockford assumes a competent reader and rewards patient and thoughtful reading rather than bulking up on exposition and screenshots. It’s very uncommon in modern writing.

The book opens by defining the syntax of JavaScript with a series of railroad diagrams that are far more enjoyable and readable than BNF:

Next it defines objects and functions and derives useful patterns for working in JavaScript. The Module pattern he gives on p41 “…can eliminate the use of global variables. It promotes information hiding and other good design practices.” It’s a nice piece of code to deal with a personal pet peeve.

After the sections on recursion, scope, closures, currying, and memoization I was surprised not to see a section on the Y combinator, which allows creating recursive anonymous functions. There’s a blog post with a nice derivation, but it seems oddly absent from the book.

More glaringly missing, though, is code to copy JavaScript objects and arrays. On p22 he writes “Objects are passed around by reference. They are never copied.” and a code comment on p64 explains how some code avoids a related bug, but Crockford never talks about how to create shallow or deep copies of objects and arrays. It is flatly bizarre to see the topic raised and warned about without any giving a solution to an interesting and common JavaScript problem. (I personally use jQuery.extend.)

After dealing with objects and functions, Crockford combines them to talk about JavaScript’s unusual prototypical inheritance, then moves on to a nice explanation of working with arrays and regexps. After talking about the standard library and giving style notes, there are a couple nice appendicies explaining what he left out and why and presenting JSLint for automated detection of common pitfalls.

There are a few odd notes like an imprecation against continue (indeed, none of his code tries to “fail fast”) that feels like it must be based on old scars inflicted by manual memory management in C/C++. The only really puzzling oddity was in the chapter surveying the standard types. He gives JavaScript reimplementations of Array’s pop, push, shift, splice, and unshift methods (but not concat, join, reverse, slice, or sort) for no discernable reason other than a mention on p98 that he’d wanted to write a self-parser in JavaScript for a chapter he contributed to another book.

I don’t think too much about these few oddities, though, it takes a certain amount of chutzpah to distill a beautiful language from a clunky, heavily-abused language and it’s harmless to see that manifest a bit of quirky style. Mostly I spent my time reading, pondering, and tinkering with the example code. There are some great examples for creating objects and working with the prototypical inheritance, and the array sorting code (p80) is an especially inspiring bit of useful code.

The only serious negative of the book is the incessant and distracting typos. There are countless small code layout issues, bad line breaks in comments (p39), weird indentation (p40), added line breaks in code (p41), occasional camelCase. There are also a few typos in the code segments that will cause weird exceptions or, worse, silent failures. If the book didn’t have so damn much useful content I’d suggest waiting for a third printing to correct these errors (I read the Sept 2008 printing, look for a [9/08] or later in the lower-right corner of the copyright page). The poor copyediting is compounded by O’Reilly’s awful errata page; you can’t filter by printing and it includes many duplicates, making for a frustrating slog through clutter to track down why a particular sample doesn’t run.



In spite of the flaws, I strongly recommend JavaScript: The Good Parts to anyone who regularly works with JavaScript. If it seems that I’m not making a good case for it, it’s because the power of the book is the enrichment gained from working through its examples and the negatives are easy to diagnose and explain. Read it. You’ll gain a new perspective of the language and refresh your toolbox with new techniques. Most importantly, you’ll stop being annoyed at writing JavaScript.