（2）第一章（入门指南）——（1）这本书讲了什么

Today's World Wide Web is a dynamic environment, and its users set a high bar for both style and function of sites. To build interesting, interactive sites, developers are turning to JavaScript libraries such as jQuery to automate common tasks and simplify
complicated ones. One reason for jQuery's popularity is its ability to assist in a wide range of tasks.
今天的万维网是一个不断变化的环境，而且他的使用者给网站的外观和功能都设定了一个很高的期待。为了建造有趣的，交互的网站，开发者们开始致力于诸如jQuery的javaScript库以便于自动完成平常的任务，简化复杂的任务。jQuery流行的一个原因就是它帮助解决许多不同问题的能力。

It can seem challenging to know where to begin because jQuery performs so many different functions. Yet, there is a coherence and symmetry to the design of the library; many of its concepts are borrowed from the structure of HTMLand Cascading Style Sheets(CSS).
The library's design lends itself to a quick start for designers with little programming experience as many of them have more experience with these technologies than they do with JavaScript. In fact, in this opening chapter, we'll write a functioning jQuery
program in just three lines of code. On the other hand, experienced programmers will also be aided by this conceptual consistency, as we'll see in the later, more advanced chapters.
了解从哪里开始可能看起来是有挑战性的，因为jQuery执行了如此多的不同的功能。然而jQuery库的设计存在连贯性和对称性，他的很多概念是从HTML和CSS中借鉴过来的。The library's design lends itself to a quick start for designers withlittle programming experience as
many of them have more experience with these technologies than they do with JavaScript.事实上，在这个开篇章节，我们将用仅仅三行代码写下一个运行的jQuery程序，另一方面，有经验的程序员也会从这种一致的概念中受益，正如我们将来会看到的更多高级的章节。

So let's look at what jQuery can do for us.

接下来我们看一下jQuery可以为我们做什么。