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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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