The third column of front-end web development, along with markup and style, is behavior, which on the Web is performed by JavaScript. The activity around HTML5 and its related APIs has also brought many new features and (dare I say it?) improvements to this scripting language, making JavaScript both easier to use casually for front-end developers and more powerful for those who really like to get into the hard-core mechanics. In the first section of this chapter, I look at some of those features.
But probably the biggest change in the world of JavaScript has been not in the language itself but in the number of libraries and frameworks that use it. There’s been a Cambrian explosion of libraries, and in the second section of this chapter, I present my Burgess Shale—a small but illuminating snapshot of what’s available.