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What Is JavaScript?

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

validation 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 was widespread. The associated 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. JavaScript is recognized as a full programming

language, capable of complex calculations and interactions, including closures, anonymous

(lambda) functions, and even metaprogramming. JavaScript has become such an important part of

the Web that even alternative browsers, including those on mobile phones and those designed for

users with disabilities, support it. Even Microsoft, with its own client - side scripting language

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

its earliest version.

The rise of JavaScript from a simple input validator to a powerful programming language could

not have been predicted. JavaScript is at once a very simple and very complicated language that

takes minutes to learn but years to master. To begin down the path to using JavaScript ’ s full

potential, it is important to understand its nature, history, and limitations.

A Short History

Around 1992, a company called Nombas (later bought by Openwave) began developing an

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

simple: a scripting language powerful enough to replace macros, but still similar enough to C (and

C++) that developers could learn it quickly. This scripting language was packaged in a shareware

product called CEnvi, which first exposed the power of such languages to developers. Nombas

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Seite 1 - COPYRIGHTED MATERIAL

What Is JavaScript? When JavaScript first appeared in 1995, its main purpose was to handle some of the input

Seite 2

Chapter 1: What Is JavaScript?10 Primarily, the BOM deals with the browser window and frames, but generally any browser - specific extension to JavaSc

Seite 3 - JavaScript Implementations

Chapter 1: What Is JavaScript?11 The numbering scheme is based on the idea that Firefox 4 will feature JavaScript 2.0, and each increment in the versi

Seite 4 - ECMAS cript Editions

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Chapter 1: What Is JavaScript?2eventually changed the name Cmm to ScriptEase. ScriptEase became the driving force behind Nombas products. When the pop

Seite 6 - **Planned

Chapter 1: What Is JavaScript?3 JavaScript Implementations Though JavaScript and ECMAScript are often used synonymously, JavaScript is much more tha

Seite 7 - Why the DOM Is Necessary

Chapter 1: What Is JavaScript?4 ECMAScript is simply a description of a language implementing all of the facets described in the specification. JavaSc

Seite 8 - DOM Levels

Chapter 1: What Is JavaScript?5 What Does ECMAS cript Conformance Mean? ECMA - 262 lays out the definition of ECMAScript conformance. To be conside

Seite 9

Chapter 1: What Is JavaScript?6 As of 2008, the five major web browsers (Internet Explorer, Firefox, Safari, Chrome, and Opera) all comply with the th

Seite 10 - JavaScript Versions

Chapter 1: What Is JavaScript?7 The Document Object Model ( DOM ) The Document Object Model (DOM) is an application programming interface (API) f

Seite 11 - Summary

Chapter 1: What Is JavaScript?8 It was decided that something had to be done to preserve the cross - platform nature of the Web. The fear was that if

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Chapter 1: What Is JavaScript?9 Additionally, other languages have developed their own DOM implementations, such as Mozilla ’ s XML User Interface La

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Stöbern Sie online oder laden Sie Datenblatt nach Software-Handbücher Wiley 978-0-470-22780-0 herunter. Wiley Professional JavaScript for Web Developers, 2nd Edition Benutzerhandbuch

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