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webpage example already discussed, the Microsoft site is likely running a server-based language such
as Microsoft Visual Basic or C# to create the webpages. JavaScript also runs in desktop widgets (notably
in Windows 8), in PDF documents, and in other similar places. This section explores how JavaScript
interacts with other client languages to provide a rich application experience.
Note JavaScript is also used as a server-side language with frameworks such as Node.js,
but JavaScript’s primary use remains as a client-side language.
htML, CSS, and JavaScript
The languages of front-end web development consist of HTML, CSS (Cascading Style Sheets), and
JavaScript. HTML provides the descriptive elements that surround content to define the layout of the
page. CSS provides the styling to make the marked-up content visually appealing. JavaScript provides
the functional and behavioral aspects to both the content and the styling. These front-end languages
are typically combined with back-end, server-side languages such as PHP, Visual Basic/C#, Java, or
Python to create a full web application.
htML
HTML is the language of the web. It’s the language developers use to create webpages. You can
create working webpages and web applications with nothing more than just HTML; however, to
today’s sophisticated users, such pages would be boring and look horrible—but they would be
webpages nonetheless. HTML is a standard or specification (two terms that are used relatively interchangeably,
in this case) defined by the World Wide Web Consortium (W3C). There are several iterations
of the HTML specification. The most current is version 5, known simply as HTML5.
HTML consists of elements enclosed in angle brackets (< and >). You already saw examples of
HTML elements in the first tutorial in the chapter. HTML elements, also called tags, describe the content
they enclose and how that content should be rendered by the browser. For example, an HTML
tag for an image element is . When the browser’s rendering engine encounters that tag, it
knows the contents of that tag should be a reference to an image file. Similarly, the tag denotes
a paragraph. Most tags, like , also have a closing or matching tag used to denote the end of that
element. In the case of , the closing tag is . Other tags use a similar syntax, with a forwardslash
(/) used to denote the end of the tag.
Tags can contain other content, called attributes, within their angle brackets. Attributes provide
additional information about the content. Some attributes are generic and can be used with all tags,
while others are specific to particular elements, such as the tag. For example, the tag
uses the src attribute to specify the location of the image file that the browser will load and render.
Here’s an tag that references an image called “SteveSuehring.jpg”:
4 Start here! Learn JavaScript