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What Is JavaScript

What Is JavaScript?

When JavaScript first appeared in 1995, its main purpose was to handle some of the input valida-

tion that had previously been left to server-side languages such as Perl. Prior to that time, a round

trip to the server was needed to determine if a required field had been left blank or an entered

value was invalid. Netscape Navigator sought to change that with the introduction of JavaScript.

The capability to handle some basic validation on the client was an exciting new feature at a time

when use of telephone modems (operating at 28.8 kbps) was widespread. Such slow speeds

turned every trip to the server into an exercise in patience.

Since that time, JavaScript has grown into an important feature of every major Web browser on

the market. No longer bound to simple data validation, JavaScript now interacts with nearly all

aspects of the browser window and its contents. Even Microsoft, with its own client-side scripting

language called VBScript, ended up including its own JavaScript implementation in Internet

Explorer from its very earliest version.

In this chapter, you will learn how and why JavaScript came about, from its humble beginnings to

its modern-day, feature-packed implementations. To be able to use JavaScript to its full potential, it

is important to understand its nature, history, and limitations. Specifically, this chapter examines:

The origins of JavaScript and client-side scripting

The different parts of the JavaScript language

The standards related to JavaScript

JavaScript support in popular Web browsers

A Short History

Around 1992, a company called Nombas began developing an embedded scripting language

called C-minus-minus (Cmm for short). The idea behind Cmm was simple: a scripting language

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