Chapter 9. Style

Here is a silly stately style indeed!

William Shakespeare, The First Part of Henry the Sixth

Computer programs are the most complex things that humans make. Programs are made up of a huge number of parts, expressed as functions, statements, and expressions that are arranged in sequences that must be virtually free of error. The runtime behavior has little resemblance to the program that implements it. Software is usually expected to be modified over the course of its productive life. The process of converting one correct program into a different correct program is extremely challenging.

Good programs have a structure that anticipates—but is not overly burdened by—the possible modifications that will be required in the future. Good programs also have a clear presentation. If a program is expressed well, then we have the best chance of being able to understand it so that it can be successfully modified or repaired.

These concerns are true for all programming languages, and are especially true for JavaScript. JavaScript's loose typing and excessive error tolerance provide little compile-time assurance of our programs' quality, so to compensate, we should code with strict discipline.

JavaScript contains a large set of weak or problematic features that can undermine our attempts to write good programs. We should obviously avoid JavaScript's worst features. Surprisingly, perhaps, we should also avoid the features that are often useful but occasionally hazardous. Such features ...

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