WEB Developer's Glossary

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• Unary Keyword Operator Group: JavaScript Operator
The unary keyword operator group is comprised of the typeof operator, delete operator and the void operator.

• Unary Plus and Minus Operator Group: JavaScript Operator
The unary plus and minus operator group is comprised of the unary_minus_operator and the unary plus operator.

• Unary Minus Operator: JavaScript Operator
The unary minus operator ( symbol: - ) returns a number that is the negated value of the operand. The operator ( - ) appears before the number operand. The unary minus operator will attempt to convert any operand to 1 when the operand is not a number. Negating -0 produces +0 and negating +0 produces -0.
The attributes of this operator are:

• Unary NOT Operator Group: JavaScript Operator
The unary NOT operator group includes operators: bitwise NOT operator, and logical NOT operator. The bitwise NOT operator works with 32-bit integer numbers and performs its operation at the bit level. The logical NOT operator works with boolean values.

• Unary Operator: JavaScript Operator
A unary operator is a JS operator with one operand. There are nine JS unary operators of which three are keyword operators.

• Unary Plus Operator: JavaScript Operator
The unary plus operator ( symbol: + ) will attempt to convert a non-numeric operand to a number. It returns "NaN" with an unsuccessful conversion. For valid number operands, it does nothing ( no operation ). Maybe its purpose is just to give balance to its sister ( unary minus operator ). It can make your code appear more readable.
The attributes of this operator are:

• URI (Uniform Resource Indicator): Web
The URI is a W3C term that encompasses both URLs and URNs. The URI is the postal address of the internet. Most of us are not involved with URN. Therefore for most users, the URL and the URI are one and the same. Also, most of us are only using a tiny peice of the URL, that is, the HTTP (Hypertext Transfer Protocol) scheme.

• URL (Uniform Resource Locator): Web
The URL is the most common form of resource identifier on the Web. Almost every URI is a URL. URLs designate a particular location of a resource on a particular server. The URL not only specifies how to locate a resource but also how to access and retreive it. There are three primary parts to a URL:
  1. the scheme
  2. the server name
  3. the resource location on named server

There are hundreds of schemes designed for the URL. Most schemes conform to the format options shown here:

URL Scheme Components and Description
Component Description Applies to
footnote ** a sample of the more popular schemes
<scheme>:// the protocol used to access the server all
<user>: user name ftp, telnet
<password>@ user password ftp, telnet
<host> the hostname of the server hosting the resource
can also be represented with the physical dotted IP address
most schemes
:<port> the network port on which the server is listening http, ftp, telnet
/<path> the local path for the target resource on the hosting server http, ftp, file
;<parms> specify input parameters ftp
?<query> used by some schemes to pass parameters to an active application http
#<frag> fragment identifier; the name of an ID attribute of an element of the target resource http

URLs have two practical reference forms: absolute and relative. The relative reference uses a base URI to resolve the complete address.

• URN (Uniform Resource Name): Web
The URN is used for identification of a Web resource. A URN is like a person's name, while a URL is like their street address. Essentially, "what" vs. "where". The URN (Uniform Resource Name) is a subset of URI. The URN assures a consistent name for a resource regardless of what server hosts the resource.

• Undefined Type: JavaScript Data Type
The type Undefined has the value called undefined.

• Undefined Value: JavaScript Value
The undefined value is a primitive value used for variables that have been declared but have not been assigned a value. The default value returned for such a variable is: undefined. The undefined value will also be returned for non existing object properties. A FSD that is coded without a return statement will return a value of undefined. In addition, when the return statement is included but specified without the optional return expression, it will return an undefined value. When a FSD is invoked but is not supplied with the required formal parameters, the missing parameters will appear as undefined values within the function body.

• Unicode: Web
Unicode provides a unique number for every character, no matter what the platform, no matter what the program, no matter what the language. Unicode has become one of the more significant recent global software technology trends. The 16-bit Unicode encoding scheme can represent every written language in common use on plant earth. Here is a summary of the advantages of Unicode: simplified encoding scheme, cost effective, increase reliability, preferred standard, increased flexibility and increased portability.

• Universal Selector: CSS Selector
The universal selector is designated with an asterisk and acts as a wildcard. The declaration in the rule that follows the asterisk is applied to all of the elements in the document provided that the element is allowed to have the property. Because of the breadth of the effect of the universal selector, it should be used with caution.

• Universal Time: JavaScript Date & Time
Universal time is the current time at Greenwich England. Universal time is based on UTC.

• URIError Subclass: JavaScript Class
The JS interpreter can throw an instance of the URIError subclass when URI decoding functions ( decodeURI() and decodeURIComponent() ) incur decoding problems. The JavaScript programmer can also create URIError instances with the URIError class constructor for the purpose of capturing the run-time exceptions. The URIError subclass inherits from the Error class that acts as a super class. The complete set of error subclasses are: EvalError, RangeError, ReferenceError, SyntaxError, TypeError, URIError.

• Used Value CSS Property Values
The used value is an intermediate value that the UA will resolve during the property value assignment process. The used value is resolved from the computed value in the third step of a four step property value assignment process. The four step value assignment process is:
  1. resolve the specified value,
  2. resolve the computed value from the specified value,
  3. resolve the used value from the computed value,
  4. resolve the actual value from the used value.

Computed values are processed as far as possible without formatting the document. Some values, however, can only be determined when the document is being laid out. For example, if the width of an element is set to be a certain percentage of its containing block, the width cannot be determined until the width of the containing block has been determined. The used value is the result of taking the computed value and resolving any remaining dependencies into an absolute value.

• User: CSS 2.1 Specification
A user is a person who interacts with a user agent to view, hear, or otherwise use a document and its associated style sheet. The user may provide a personal style sheet that encodes personal preferences.

• User Agent: CSS 2.1 Specification
A user agent is any program that interprets a document written in the document language and applies associated style sheets according to the terms of this specification. A user agent may display a document, read it aloud, cause it to be printed, convert it to another format, etc. An HTML user agent is one that supports the HTML 2.x, HTML 3.x, or HTML 4.x specifications. A user agent that supports XHTML, but not HTML (as listed in the previous sentence) is not considered an HTML user agent for the purpose of conformance with this specification.

• User Defined Class: JavaScript OOD
In formal OOD terms, we can create a custom type (or class). The user defined class type can then be used to instantiate objects of that class type. Object instances will inherit the properties and methods of the custom class type. We can build a class constructors, class methods and other properties for our class. JS will automatically provide a prototype object for our class. Thereby, we can build instance properties for our class by adding them to the prototype object representing our custom class.

• User Interface Style Group: CSS Property
The user interface style group is one of eleven property style groups that help define the total CSS property set. The user interface style group contains properties that change the look of the user's cursor and other properties that provide outlines. Outlines are like borders but they do participarte in document flow and they can be nonrectangular. Also, outlines can coexist with borders on the same element. The complete list of properties that comprise the user interface style group are:

• UTC (Coordinated Universal Time): JavaScript Date & Time
Coordinated Universal Time is a high-precision atomic time standard. Time zones around the world are expressed as positive or negative offsets from UTC. UTC is the current term for what was commonly referred to as Greenwich Meridian Time (GMT). Zero (0) hours UTC is midnight in Greenwich England, which lies on the zero longitudinal meridian. Universal time is the current time at Greenwich England. Universal time is based on a 24 hour clock.


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