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Professional: JavaScript® for Web Developers, Third Edition by Nicholas C. Zakas

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Chapter 9

Client Detection

What’s in This Chapter?

  • Using capability detection
  • The history of user-agent detection
  • When to use each type of detection

Although browser vendors have made a concerted effort to implement common interfaces, the fact remains that each browser presents its own capabilities and flaws. Browsers that are available cross-platform often have different issues, even though they are technically the same version. These differences force web developers to either design for the lowest common denominator or, more commonly, use various methods of client detection to work with or around limitations.

Client detection remains one of the most controversial topics in web development. The idea that browsers should support a common set of functionality pervades most conversations on the topic. In an ideal world, this would be the case. In reality, however, there are enough browser differences and quirks that client detection becomes not just an afterthought but also a vital part of the development strategy.

There are several approaches to determine the web client being used, and each has advantages and disadvantages. It’s important to understand that client detection should be the very last step in solving a problem; whenever a more common solution is available, that solution should be used. Design for the most common solution first and then augment it with browser-specific solutions later.

Capability Detection

The most commonly used and widely accepted form of client ...

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