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Netscape Visual JavaScript is a component-based visual development tool for the Netscape Open Network Environment (ONE) platform. It is primarily intended for use by application developers who want to build cross-platform, standards-based, web applications from ready-to-use components with minimal programming effort. The applications are based on HTML, JavaScript, and Java.
Because Visual JavaScript is a visual development environment, you do not need to know these languages to create applications. Instead, you can use the provided components, specifying their behavior and interaction visually. However, an understanding of some of the fundamentals behind Visual JavaScript will help as you move from basic to more complex application development.
This chapter provides a high-level overview of the main features of the product available in this release, system requirements, an introduction to JavaScript, and information about the component model used.
Feature Overview
These are the major features of Visual JavaScript:
System Requirements
Visual JavaScript is designed to be platform independent. It has been tested on various system, including Windows 95, Windows NT 4.0, and Solaris 2.5.1. For a complete, up-to-date list of supported operating systems, refer to the Release Notes.
You can develop and run Visual JavaScript applications with Netscape Enterprise Server 2.0, 3.0, or 3.5. For client-side JavaScript debugging, you must have Communicator 4.0 or a later version. Depending on which components you use in your application, your end user might need to have a Java- or JavaScript- enabled browser.
These are the elements of a Visual JavaScript development environment:
In general, Netscape recommends that you develop applications on a system other than your deployment (production) server, because development consumes resources (for example, communications ports, bandwidth, processor cycles, and memory). Development might also disrupt end-user applications that have already been deployed.
In addition, if your application uses Enterprise Server's LiveWire Database Service, you need the following:
About JavaScript
JavaScript is Netscape's cross-platform, object-based scripting language for client and server applications; it is the glue that binds together the components you use to build applications with Visual JavaScript. JavaScript lets you create applications that run over the Internet. Using JavaScript, you can create dynamic HTML pages that process user input and maintain persistent data using special objects, files, and relational databases. Through JavaScript's LiveConnect functionality, your applications can access Java and CORBA distributed object applications.
Some developers choose to use JavaScript solely on the client (in Navigator or another web browser). This is called client-side JavaScript (or Navigator JavaScript), and it encompasses the core language plus extras such as the predefined objects only relevant to running JavaScript in a browser. Larger-scale applications frequently have more complex needs, such as communicating with a relational database, maintaining application state across multiple client requests, or performing file manipulations on a server. For these more demanding situations, Netscape web servers contain server-side JavaScript. Some aspects of the core language act differently when run on a server. In addition, to support the increased performance demands in these situations, server-side JavaScript is first compiled.
See JavaScript Reference and Writing Server-Side JavaScript Applications for more information about the JavaScript language.
Understanding the Component Model
Components, the building blocks you use to construct your crossware applications, are packages of re-usable Java or JavaScript code that generate HTML, as well as blocks of re-usable HTML code. Component code can define visual elements (HTML tags or Java applets on the client) that the end user can see and interact with on the page, such as buttons and tables. It can also define nonvisual objects that you can see in the development environment but that are not visible to the end user at run time. Nonvisual components are used to store data, state information, and logic for an application.
Visual JavaScript components are based on the JavaBeans component model, which was developed by Sun Microsystems. The model is extended to apply it to JavaScript. JavaBean and JavaScript Bean components can be written and added to Visual JavaScript, and some components can be generated automatically. For example, when you choose to install a component from a CORBA object file, the system generates a JavaScript Bean component from IDL files that make use of IIOP to communicate over an object request broker.
Components are self-contained objects whose interface to their application environment consists of properties, methods, and events.
The code that implements components can run on the client, the server, or both. The source code defines a design-time object in the Visual JavaScript development environment when you use the component in your application. You then use the Visual JavaScript tools (such as the Page Editor, Inspector, and Connection Builder) to specify what the component should do at run time. When you run the finished application, both visual and non-visual objects are defined in the runtime environment according to your specifications. The runtime objects are usually smaller and faster than design-time objects, since less logic and data are required to do a specific task than to program how to do it.
The source code that defines components is kept in the following kinds of files:
When you use a component, the required component files are automatically added to your project, so that they are deployed with your HTML pages to the web server and compiled into an application.
See the Netscape Component Developer's Guide for more information about the structure of components and how to build your own.
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Last Updated: 11/06/97 13:24:47
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