Adobe Dreamweaver CC 2014 v.13 - Manual (Page 513)

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You can also define expressions for if and multiple-if conditions. When an expression is used in a conditional statement, Dreamweaver evaluates it
as true or false. If the condition is true, the optional region appears in the template-based document; if it is false, it doesn’t appear.
You can define expressions in Code view or in the Optional Region dialog box when you insert an optional region.
In Code view, there are two ways to define template expressions: use the comment or @@(your
expression)@@. When you insert the expression in the template code, an expression marker appears in Design view. When you apply the
template, Dreamweaver evaluates the expression and displays the value in the template-based document.
Template expression language
The template expression language is a small subset of JavaScript, and uses JavaScript syntax and precedence rules. Use JavaScript operators to
write an expression like this:
@@(firstName+lastName)@@
The following features and operators are supported:
numeric literals, string literals (double-quote syntax only), Boolean literals (true or false)
variable reference (see the list of defined variables later in this section)
field reference (the “dot” operator)
unary operators: +, -, ~, !
binary operators: +, -, *, /, %, &, |, ^, &&, ||, <, <=, >, >=, ==, !=, <<, >>
conditional operator: ?:
parentheses: ()
The following data types are used: Boolean, IEEE 64-bpc floating point, string, and object. Dreamweaver templates do not support the use of
JavaScript “null” or “undefined” types. Nor do they allow scalar types to be implicitly converted into an object; thus, the expression
"abc".length would trigger an error, instead of yielding the value 3.
The only objects available are those defined by the expression object model. The following variables are defined:
_document Contains the document-level template data with a field for each parameter in the template.
_repeat Only defined for expressions which appear inside a repeating region. Provides built-in information about the region
_index The numerical index (from 0) of the current entry
_numRows The total number of entries in this repeating region
_isFirst True if the current entry is the first entry in its repeating region
_isLast True if the current entry is the last entry in its repeating region
_prevRecord The _repeat object for the previous entry. It is an error to access this property for the first entry in the region.
_nextRecord The _repeat object for the next entry. It is an error to access this property for the last entry in the region.
_parent In a nested repeated region, this gives the _repeat object for the enclosing (outer) repeated region. It is an error to access this
property outside of a nested repeated region.
During expression evaluation, all fields of the _document object and _repeat object are implicitly available. For example, you can enter title
instead of _document.title to access the document’s title parameter.
In cases where there is a field conflict, fields of the _repeat object take precedence over fields of the _document object. Therefore, you
shouldn’t need to explicitly reference _document or _repeat except that _document might be needed inside a repeating region to reference
document parameters that are hidden by repeated region parameters.
When nested repeated regions are used, only fields of the innermost repeated regions are available implicitly. Outer regions must be
explicitly referenced using _parent.
Multiple If condition in template code
You can define template expressions for if and multiple-if conditions. This example demonstrates defining a parameter named "Dept", setting an
initial value, and defining a multiple-if condition which determines which logo to display.
The following is an example of the code you might enter in the head section of the template:
The following condition statement checks the value assigned to the Dept parameter. When the condition is true or matches, the appropriate image
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