JavaScript: The Definitive Guide, Fourth Edition

Chapter 1. Introduction to JavaScript

JavaScript is a lightweight, interpreted programming language with object-oriented capabilities. The general-purpose core of the language has been embedded in Netscape, Internet Explorer, and other web browsers and embellished for web programming with the addition of objects that represent the web browser window and its contents. This client-side version of JavaScript allows executable content to be included in web pages -- it means that a web page need no longer be static HTML, but can include programs that interact with the user, control the browser, and dynamically create HTML content.

Syntactically, the core JavaScript language resembles C, C++, and Java, with programming constructs such as the if statement, the while loop, and the && operator. The similarity ends with this syntactic resemblance, however. JavaScript is an untyped language, which means that variables do not need to have a type specified. Objects in JavaScript are more like Perl’s associative arrays than they are like structures in C or objects in C++ or Java. The object-oriented inheritance mechanism of JavaScript is like those of the little-known languages Self and NewtonScript; it is quite different from inheritance in C++ and Java. Like Perl, JavaScript is an interpreted language, and it draws inspiration from Perl in a number of places, such as its regular expression and array-handling features.

This chapter provides a quick overview of JavaScript; it explains what ...