WEB Developer's Glossary



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• Data Types: Core ECMAScript
Core ECMAScript provides JavaScript with two general kinds of data types. There are five primitive types and three reference types. The set of data types will govern the types of values (data) that can be represented within the language. Data types in JavaScript are not explicitly specified, thus, JavaScript is a weakly typed language. Weak typed languages are also referred to as dynamically typed and untyped languages.

• Data Types: CSS
CSS property values often conform to one or more CSS data types. The data type specifies the nature of the value that can be assigned to the property. CSS property values can also be keywords such as "inherit". The CSS property definition uses the greater than and less than sign to enclose a data type reference. The CSS data types are itemized and can be refereced here:

• Data Types: HTML
Each HTML attribute value has an associated data type. The data type specifies the nature of the value that can be assigned to the attribute. All attributes must be assigned a value (an implicit rule with HTML, an explicit rule with XHTML).

• Data Types: SGML
The HTML specific data types are defined in the HTML application using SGML constructs. These constructs are specified in the HTML DTDs where the SGML data type is the building block for each HTML data type. The SGML data type are: CDATA, PCDATA, ID, NAME, IDREF, IDREFS, NUMBER, NMTOKEN and NMTOKENS.

• Date and Time: JavaScript Terms
Representing and working with dates and times is a common feature with most computer languages. JS dates and times have the following characteristics and features:
  • Date class: dates and times are facilitated with the Date class.
  • Date Methods: The Date class has over 40 instance methods and two class methods.
  • Internal date: The JS date and time is represented by a single internal number. This number is relative to a fixed starting point in time and is accurate to the millisecond.
  • Dates in JS do not have there own unique data type.
  • Date literal formats are not provided.
  • Date class constructor: JS date and times are created with the Date class constructor. The constructor can take varing arguments; 1) the internal number, 2) a date string or 3) date and time parts.
  • JS date and time is represented in UTC time.


• Date Class: JavaScript Class
The Date class is a JS Native Class that supports JS date and time. Object instances of the Date class have access to the properties and methods of the Date class. With JS, the Date class does not have an associated data type (many languages have a date data type). Therefore, there is no such thing as a date literal with JS. You create a Date object via the Date class constructor. See our link for class for the distinction between the terms "class" and "object".

• Date Object: JavaScript Object
The Date object is a instance of the Date class. A Date object can be declared and initialized via the Date class constructor. JS does not support Date literal forms. See our link for class for the distinction between the terms "class" and "object".

• Date & Time Parts: JavaScript Date & Time
The internal date can be retrieved using a number of Date object methods. Date and time methods will retrieve the following parts: Day of Week, Month, Day of Month, hour (military), minute, second, Time Zone, Century and Year.

• Deadzone: HTML
An area in the image that has its coordinates defined but there is no related hyperlink. Use the NOHREF attribute instead of the HREF attribute to define a deadzone.

• Decrement Operator: JavaScript Operator
The decrement operator ( symbol: -- ) will decrement a variable by one. The decrement operator has two variations; the pre-decrement operation. and the post-decrement operation.

• delete Operator: JavaScript Operator
The unary delete operator ( keyword: delete ) attempts to delete array elements, variables or object properties that are specified in its operand. Its operand takes the lvalue. Some built-in and host properties are immune from deletion. Deletion causes the subject of the operand to cease to exist. The delete operator will return a boolean indicating operation success of failure.
The attributes of this operator are:

• delete Statement: JavaScript Expression Statement
The delete statement is a statement that contains a delete operator. A delete statement is an expression statement where the side effect causes the the subject of the operand to be deleted. The operator also returns a boolean: true if successful, otherwise false.

• Deprecated: W3C
A term used by the W3C to describe features of a given W3C specification that have become outdated and may become obsolete in future releases. User agents are to continue to support deprecated items. Deprecate HTML items are still supported with the Transitional Document Type Definition (DTD). Note: the Frameset DTD also provide support for deprecated items in HTML.

• Deprecated: JavaScript Term
ECMAScript and JavaScript have language features that become outdated because new features do a better job or conform to future directions in Web technologies. Like with W3C deprecated items, browsers should continue to provide support for JS deprecated features.

• Descendant: CSS 2.1 Specification
An element A is called a descendant of an element B, if either (1) A is a child of B, or (2) A is the child of some element C that is a descendant of B.

• Descendant Selector: CSS Selector
A descendant selector's pattern is made up of two or more selectors separated by whitespace. The element on the left holds a higher position in the document tree than the element on the right. The element on the right is a descendant of the element in the left. The element on the left is an ancestor of the element on the right. The descendant selector is one of three relational selectors. The three relational selectors (descendant, child and sibling) all require a combinator. The combinator serves as a pattern separator and also determines the relationship of the elements in the pattern. The combinator for the descendant selector is the "space" and is referred to as whitespace in the CSS specification. The "space" combinator can be translated as: "is a descendant of" when reading from right to left in the pattern. See selector patterns for formats.

• DHTML Web
The Dynamic Hypertext Markup Language is a term used to describe Web pages that contain dynamic effects. DHTML is not a stand alone technology. It is a term used to describe the interaction of three technologies (HTML, CSS and JavaScript) that together achieve dynamic effects on a Web page.

• Division Operator: JavaScript Operator
The division operator ( symbol: / ) will divide its first operand by its second operand. Results are unpredicable when one or both operands are non-numeric. Division by zero yields infinity. Special rules apply to NaN numbers and Infinity numbers.
The attributes of this operator are:

• DOCTYPE: HTML and XML
The DOCTYPE declaration tells the processing user agent what DTD to use while rendering a given document. The DOCTYPE declaration appears on the first line of your HTML document and is identified with the "<!DOCTYPE" keyword.

• Document Language: CSS 2.1 Specification
The document language is the encoding language of the source document (e.g., HTML, XHTML or SVG). CSS is used to describe the presentation of document languages and CSS does not change the underlying semantics of the document languages.

• Document Object Model DOM
The Document Object Model is a W3C specification. The DOM provides a standard set of objects for representing HTML and XML documents. In addition, the DOM provides a standard model of how these objects may be combined and a standard interface for accessing and manipulating them. The DOM Level 1 specification consists of two parts. An external link to DOM (HTML) Level 1 describes objects and methods specific to HTML documents. An external link to DOM (Core) Level 1 defines a set of objects and interfaces for accessing and manipulating document objects.

• Document Tree, The CSS
The Document Tree is the relational structure of elements in the source document. It is a top-down hierarchy structure. Elements within an HTML document can be formed into a document tree. Each element has a unique tree relationship with its immediate higher element "parent" and its' immediate lower element "child". Every element within a document tree has exactly one parent, except for the root of the tree, which has none. Viewing an HTML document in its totality, the root element is the HTML start tag. The document tree is the foundation for style and attribute inheritance and style cascading.
CSS 2.1 Specification
The tree of elements encoded in the source document. Each element in this tree has exactly one parent, with the exception of the root element, which has none.

• Dot Operator: JavaScript Operator
JavaScript has a dot operator ( symbol: • ) mandating the highest priority of 15. The operator symbol is a period. This operator is used to provide access to properties or methods of objects. The binary dot operator expects an object operand for the left operand and an identifier operand as its right operand.
The attributes of this operator are:

• do/while Statement JavaScript Statement
The do/while statement is one of JavaScript's program control structures. Both do and while are keywords in the JS language. The do/while statement has two syntactical components. First, the do clause specifies the block statement that represents the loop body. Next, the while trailer clause contains a conditional expression that is enclosed in parentheses. The expression is called a loop condition. The loop condition acts as a decision maker and it is a logical expression that evaluates to a boolean value. The condition that will terminate the loop is tested on each iteration. As long as the test remain true, the loop is executed one more time. Once the loop condition tests to be false the loop is terminated. Once terminated, the program flow procedes to the next sequencial statement immediately after the while statement. The loop body is responsible for altering the test condition in the loop conditional expression, otherwise an endless loop will occur. The while statement and the do/while statements are similar, however, note that the do/while structure will always process the loop body at least once (the first time through is a given).

• DTD: HTML and SGML
Document Type Definition: The DTD defines the syntax of a markup language. The DTD is built from a SGML declaration.

• Dynamic Selectors: CSS Selector
The pseudo-class dynamic selector's are influenced by user interaction with the document's elements. They are dynamic in that there behavior is only temporary and may change at random depending on the user's actions. See selector patterns for formats. The three dynamic selectors all require a colon placed in front of the pseudo-class keyword. The three dynamic selectors are given here:
  • :hover The :hover pseudo-class applies while the user points to an element, but does not activate it. When the user's pointing device leaves the element, the element changes back to the previous style.
  • :active The :active pseudo-class applies while an element is being activated by the user. The element will return to it's original style once the pointing device is released.
  • :focus The :focus pseudo-class applies while an element has the focus. The onfocus event occurs when an element receives focus either by the pointing device or by tabbing navigation.














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