By Rick Darnell
Terms
While not necessarily JavaScript objects or keywords, the following items can
help in your understanding of JavaScript and how it works. These are the general
terms that are used in most discussions about JavaScript and its implementation.
Cookie A special object containing state/status information
about the client that can be accessed by the server. Included in that state
object is a description of the range of URLs for which that state is valid. Future
HTTP requests from the client falling within a range of URLs described within the
state object will include transmission of the current value of the state
object from the client back to the server. This simple form of data storage allows
the server to provide personalized service to the client. Online merchants can store
information about items currently in an electronic shopping basket, services can
post registration information and automate functions such as typing a user ID, and
user preferences can be saved on the client and retrieved by the server when the
site is contacted. For limited-use information, such as shopping services, it is
also possible to set a time limit on the life of the cookie information.
CGI scripts are typically used to set and retrieve cookie values. To generate
the cookie requires sending an HTTP header in the following format:
Set-Cookie: NAME=Value;
[EXPIRES=date;] [PATH=pathname;]
[DOMAIN=domainname;] [SECURE]
When a request for cookie information is made, the list of cookie information
is searched for all URLs which match the current URL. Any matches are returned in
this format:
cookie: NAME1=string1;
NAME2=string2; ...
Cookie was an arbitrarily assigned name. For more information about the
cookie and its function, see http://home.netscape.com/newsref/std/cookie_spec.html.
Event Handler Attributes of HTML tags embedded in documents.
The attribute assigns a JavaScript command or function to execute when the event
happens.
Function A user-defined or built-in set of statements that perform
a task. It can also return a value when used with the return statement.
Hierarchy Navigator objects exist in a set relation to each
other that reflects the structure of an HTML page. This is referred to as instance
hierarchy because it only works with specific instances of objects, rather than
general classes. The window object is the parent of all other Navigator
objects. Underneath window, location, history, and document
all share precedence. Document includes forms, links, and anchors.
Each object is a descendant of the higher object. A form called orderForm
is an object, but is also a property of document. As such, it is referred
to as document.orderForm.
Java An object-oriented, platform-independent programming language
developed by Sun Microsystems and used to add additional functionality to Web pages.
Programming in Java requires a Java Development Kit with compiler and core classes.
Although Java started out as a language intended for writing Web applets, more and
more stand-alone Java applications are being created.
JavaScript A scripting language developed by Netscape for HTML
documents. Scripts are performed after specific user-triggered events. Creating JavaScript
Web documents requires a text editor and compatible browser.
Literal An absolute value not assigned to a variable. Examples
include 1, 3.1415927, "Bob", true.
Method A function assigned to an object. For example, bigString.toUpperCase()
returns an uppercase version of the string contained in bigString.
Object A construct with properties that are JavaScript variables
or other objects. Functions associated with an object are known as the object's
methods. You access the properties of an object with a simple notation:
objectName.propertyName
Both object and property names are case sensitive.
Operator Performs a function on one or more operands or variables.
Operators are divided into two classes: binary and unary. Binary operators need two
operands, and unary operands can operate on a single operand. For example, addition
is a binary operand:
sum = 1 + 1
Unary operands are often used to update counters. The following example increases
the variable by 1:
counter++
Property Used to describe an object. A property is defined by
assigning it a value. There are several properties in JavaScript that contain constants:
values that never change.
Script One or more JavaScript commands enclosed with a <script>
tag.
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