It would be hard to find a web application that doesn’t depend on a library—at least, not one of any consequence. Libraries are the epitome of not redefining the wheel. In fact, like wheels, there are libraries of every shape, size, and color out there. Yes, even color comes into play when you consider that many libraries include themes you can use to dress up your site. Consequently, it’s likely that you’ve already spent a fair amount of time working with libraries in some way. In fact, a number of the book examples in earlier chapters relied on libraries simply because rewriting the code from scratch doesn’t make sense.
This chapter doesn’t try to persuade you about the value of using libraries. You’ve likely already sold yourself on their benefit. However, you might not have considered all the ramifications of using someone else’s code in your application. There are always consequences to using libraries. The goal is to use libraries safely so that you get all the benefits of relying on someone else’s code without creating any major security holes in your application. (Be assured, you do create some security holes; it’s impossible to avoid it.)