WEB Developer's Glossary

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• Value Group: CSS Value
Value groups will appear in the value portion of a CSS property value definition. The value group is expressed and enclosed with < > symbols. The value group is a set of value options that are applicable for the given property. All value groups are a shorthand version of the valid set of values for the given property, that is, the value group expands into the valid set of values. The CSS value groups and their expansion are:

• Value Type: CSS Value
The value type of a CSS property designates the legal values for a property. A given property may incorporate value alternatives, gouping and other options all expressed with a value declaration syntax. Value types can be expressed with:

• var Statement JavaScript Statement
The var statement is the syntax that allows JS to declare and define a variable. A variable allocates storage space for new data. var is a keyword in the JS language. The var statement consists of the following syntactical components; from left to right:
  • var keyword: acts as a operator (not offically a JS operator) in that it allocates a unit of storage, associates it with a name and defines a data value.
  • identifier: declares a name for the variable.
  • assignment operator: the assignment operator assigns the data value to the identifier.
  • literal: the literal represents the data value to be assigned (initialize).
The var statement performs the variable declaration (naming) and the optional initialization (assigning a data value to the variable). See the link for variable for further characteristics of a JS variable.

• Variable: JavaScript Term
A variable represents data at a given storage location. In JS, a variable has the following characteristics:
  • named: each variable is named (identifier).
  • typed: each variable has a data type. The data type may be of a primitive type or a reference type.
  • weakly typed: JS variables are weakly typed. A variables data type is determined dynamically at initialization time.
  • type conversion: once initialized, a variable's value may be changed. Any new value assigned to a variable will cause the variable to be retyped.
  • uninitialized: a variable that has not been initialized will have a value of undefined.
  • deletion (not): once declared, a variable can not be deleted (the value - yes, the name - no).
  • scope: each variable has a specific scope at any given time.
  • property: variables declared inside a method are more commonly referred to as properties in JS.

• Viewpoint: CSS 2.1 Specification
User agents for continuous media generally offer users a viewport (a window or other viewing area on the screen) through which users consult a document. User agents may change the document's layout when the viewport is resized. When the viewport is smaller than the area of the canvas on which the document is rendered, the user agent should offer a scrolling mechanism. There is at most one viewport per canvas, but user agents may render to more than one canvas (i.e., provide different views of the same document).

• Visual Formatting Model: CSS Property
The visual formatting model determines how user agents process the document tree for visual media. Visual media represents both continuous and paged media types. The visual formatting model and the box model work together to determine document layout and flow. The governing principles of the visual formating model are:
  • box dimensions: of the content area and surrounding padding, border and margin areas
  • box type: block boxes, inline boxes and run-in boxes
  • positioning scheme: normal flow, float and absolute positioning
  • relationship of the document tree: see tree relationships
  • external information: viewpoint size, image dimensions
Other than the aural style properties, all CSS properties of the CSS 2.1 Specification support visual media. However those properties dedicated to document layout, positioning and flow (covered in sections 9, 10 and 11 of the CSS 2.1 Specification) for our purposes are represented by two groups; the positioning style group and the visual style group. The latter group being a bit of a 'catch-all' group.

• Visual Media Group: CSS Property
The visual media group represents those CSS properties that prepare a document's content to be experienced primarily using the eyes. The visual media group belongs to the sensory group that includes the groups: audio, speech and tactile. The visual media group is appropriate for all of the following media types: handheld, print, projection, screen, tty and tv. There are ten CSS properties ( width, min-width, max-width, height, min-height, max-height, vertical-align, overflow, clipping and visibility) that represent this group.

• Visual Style Group: CSS Property
The visual style group is one of eleven property style groups that help define the total CSS property set. The visual style group contains the properties that represent a portion of the properties that support the visual formatting model. The remainder of the properties for the visual formatting model are represented with the positioning style group. The complete list of properties that comprise the visual style group are:

• void Operator: JavaScript Operator
The unary void operator ( keyword: void ) discards the operands original value and replaces it with an undefined value. The operand to the void operator may be of any type.
The attributes of this operator are:

• Void Statement: JavaScript Expression Statement
The void statement is a statement that contains a void operator. A void statement is an expression statement.The left hand side operand's value is altered to "undefined". The side effect of the expression statement is that the void's unary operand's value is altered.


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