JavaScript 2.0-The Complete Reference, Second ... - freecodingtutorial

within Web sites. Most JavaScript programmers use those features they find convenient and
leave the major OOP features to those writing full-fledged Web applications.
Summary
JavaScript provides four types of objects: user-defined, built-in, browser, and document. This
chapter focused on the fundamental aspects of all objects, as well as the creation and use of
user-defined objects. JavaScript is a prototype-based, object-oriented language. New object
instances are created with constructors, objects that initialize the properties of new instances.
Every object has a prototype property that reflects the prototype of the constructor used to
create it. When an object property is accessed, the interpreter first checks the object‘s instance
properties for the desired name. If it is not found, the properties of the object‘s prototype are
checked. This process repeats recursively until it has worked up the chain of inheritance to the
top-level object. Most of the time in JavaScript, the creation and management of the objects is
straightforward, and programmers are freed from such headaches as memory management.
While user-defined objects can be used to create much more modular and maintainable scripts,
many JavaScript programmers do not really use them, given the simplicity of their scripts.
Instead, the various built-in, browser, and document objects are utilized. The next chapter
begins the examination of such objects, starting with built-in objects, particularly Array, Math,
Date, and String.
Chapter 7: Array, Date, Math, and Type-Related
Objects
This chapter discusses in detail the capabilities of JavaScript‘s built-in objects, particularly
Array, Date, and Math. We will also look into the built-in objects related to the primitive types,
such as Boolean, Number, and String, as well as the mysterious Global object. Notably
missing from this chapter is the RegExp object, which requires a significant amount of
explanation and is the subject of the next chapter. For each object covered in this chapter, the
focus will be primarily on those properties most commonly used and supported by the major
browsers. The complete list of properties of the built-in objects, including version information,
can be found in Appendix B. So let‘s start our overview of these built-in objects, proceeding in
alphabetical order, starting from Array and ending in String.
Array
Arrays were introduced in Chapter 3 as composite types that store ordered lists of data. Arrays
may be declared using the Array() constructor. If arguments are passed to the constructor, they
are usually interpreted as specifying the elements of the array. The exception is when the
constructor is passed a single numeric value that creates an empty array, but sets the array‘s
length property to the given value. Three examples of array declaration are
var firstArray = new Array();
var secondArray = new Array("red", "green", "blue");
var thirdArray = new Array(5);
The first declaration creates an empty array called firstArray. The second declaration creates a
new array secondArray with the first value equal to ―red,‖ the second value equal to ―green,‖
and the last value equal to ―blue.‖ The third declaration creates a new empty array thirdArray
whose length property has value 5. There is no particular advantage to using this last syntax,
and it is rarely used in practice.
JavaScript 1.2+ allows you to create arrays using array literals. The following declarations are
functionally equivalent to those of the previous example: