JavaScript Defined

JavaScript is a scripting language that’s used to add interactivity and dynamic behaviors to web pages and applications. JavaScript can interact with other components of a web page, such as HTML and CSS, to make them change in real time, or respond to user events.You’ll undoubtedly have seen JavaScript in the source code of web pages. It might have been inline code in an HTML element, like this:

It might have appeared as a script element linking to another file:

Or it may have had code directly inside it:

Don’t worry about the differences between these snippets yet. There are quite a few ways—both good and bad—in which we can add JavaScript to a web page.We’ll look at these approaches in detail later in this chapter.

JavaScript was developed by Netscape and implemented in Netscape 2, although it was originally called LiveScript. The growing popularity of another language, Java, prompted Netscape to change the name in an attempt to cash in on the connection, as JavaScript provided the ability to communicate between the browser and a Java applet.

But as the language was developed both by Netscape, in its original form, and by Microsoft, in the similar-but-different JScript implementation, it became clear that web scripting was too important to be left to the wolves of vendor competition. So, in 1996, development was handed over to an international standards body called ECMA, and JavaScript became ECMAScript or ECMA-262.

Most people still refer to it as JavaScript, and this can be a cause of confusion: apart from the name and similarities in syntax, Java and JavaScript are nothing alike.