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文件名称：JavaScript for Absolute Beginners.pdf
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更新时间：2022-09-05 09:40:17
JavaScript Absolute Beginners
In the 2005 film adaptation of The Hitchhiker’s Guide to the Galaxy by Douglas Adams, aliens demolish
the earth to make way for a hyperspace expressway. Our demise could have been averted insofar as the
demolition proposal had been on file at local planning offices worldwide for some time. However, no
one complained during the public comment period.
Like construction proposals, no one ever bothers to read the preface to a programming book.
Typically, that’s mostly harmless, but not for this book. Though you won’t be vaporized into star dust for
jumping to Chapter 1 or later, you’ll be befuddled for not having downloaded and familiarized yourself
with Firebug, our tool for learning JavaScript.
JavaScript is a beginner-friendly programming language available in browsers such as Internet
Explorer, Firefox, Safari, Opera, and Chrome. Those browsers contain a JavaScript interpreter to parse
and run your JavaScript programs, which you write in plain text with a text editor. So, you can use the
same text editor that you code your XHTML and CSS with.
JavaScript derives its syntax, which is to say its grammar, from the ECMAScript standard and its
features for manipulating XHTML, CSS, and HTTP from the DOM standard. Typically, JavaScript
interpreters implement ECMAScript and DOM in separate libraries. So, just as your brain has left and
right lobes, a browser’s JavaScript brain has ECMAScript and DOM lobes.
In the first six chapters, we’ll converse with the ECMAScript lobe. Then we’ll converse with the DOM
lobe for a couple of chapters. I guess you could say we’ll be picking a JavaScript’s brain one lobe at a
time—ECMAScript and then DOM, with Firebug. Finally, in the last two chapters, we’ll hand-code an
uber-cool JavaScript program with our preferred text editors. But we’ll never make it through Chapters
1–8 without Firebug. So, our first order of business will be to have you download and familiarize yourself
with Firebug, a free add-on to Firefox for Windows, Mac, or Linux.
Obviously, prior to installing a Firefox add-on like Firebug, you need to have Firefox. Note that
Firefox is a free web browser for Windows, Mac OS X, or Linux. To download Firefox, go to
www.mozilla.com, and click the Download Firefox – Free button, as displayed in Figure 1. Then follow the
wizard to install Firefox on your computer.
Open Firefox, and then download the Firebug add-on from www.getfirebug.com. Simply click Install
Firebug for Firefox button in the top-right corner, as shown in Figure 2. Then follow the wizard, granting
permission to install the add-on if prompted by Firefox.