JavaScript and Client-Side Code

Scripts allow HTML forms to process input as it is entered: to ensure that values conform to specified patterns, to check consistency between fields and to compute derived fields.

Scripts can also be used to simplify authoring of active documents. The behaviour of objects inserted into HTML documents can be tailored with scripts that respond to events generated by such objects. This enables authors to create compelling and powerful web content. This specification covers extensions to HTML needed for client-side scripting, but leaves out the architectural and application programming interface issues for how scripting engines are implemented and how they communicate with the document and other objects on the same page.

Client Side Code: This is code/routines that are not processed at all by the server. Code is written in scripts (javascript usually) - plain text commands that instruct the client to do something. Generally used for performing dynamic effects, such as image rollovers, or displaying message boxes, or even validation of data entered into a form (i.e. email address is in the format of an email address ... contains the @ symbol).

JavaScript

JavaScript (sometimes abbreviated JS) is a prototype-based scripting language that is dynamic, weakly typed and has first-class functions. It is a multi-paradigm language, supporting object-oriented, imperative, and functional programming styles.

JavaScript was formalized in the ECMAScript language standard and is primarily used in the form of client-side JavaScript, implemented as part of a Web browser in order to give enhanced user interfaces and dynamic websites. This enables programmatic access to computational objects within a host environment.

JavaScript uses syntax influenced by that of C. JavaScript copies many names and naming conventions from Java, but the two languages are otherwise unrelated and have very different semantics. The key design principles within JavaScript are taken from the Self and Scheme programming languages.