VBScript Reference Manual for InduSoft Web Studio

InduSoft Web Studio VBScript Reference Manual
This relationship between type Variant and the various data subtypes is explained by the fact that
VBScript uses what is called “late-bound” typing, meaning that the data subtype is determined at
runtime by its usage or by a function. At runtime, the Parser in the VBScript Scripting Engine will
determine the data type required and allocate storage accordingly, then execute the statements or
functions accordingly for the data type. Microsoft reportedly implemented VBScript with late-bound data
typing in order to improve execution speed.
In its simplest form, a Variant contains either numeric or string data. A Variant behaves as a number
when you use it in a numeric expression and as a string when you use it in a string expression. That is,
if you are working with data that looks like numbers, VBScript assumes that it is a number and does
what is most appropriate for numbers. Similarly, if you're working with data that can only be string data,
VBScript treats it as string data. If you enclose a variable in quotation marks (" "), you will always make
the variable behave as a strings. When variables are initialized, a numeric variable is initialized to 0 and
a string variable is initialized to a zero-length string ("").
A variable that refers to an object must be assigned to an existing object using the Set statement
before it can be used. Until it is assigned an object, the declared object variable has the special value
Nothing.
Beyond simple numeric or string classifications, a Variant can be distinguished by the specific nature of
data it contains or represents. For example, numeric information can represent date or time. When the
variable is used with other date or time variables or operations, the result is always expressed as a date
or a time.
The Variant type is best thought of as a super data type which includes all the data subtypes. You can
change a variable’s value and subtype at runtime by assigning a new value to the variable from one
previously assigned to it. For example:
Dim x
x = “message1” ‘ x would be a string subtype
x = 1 ‘ x would now become a integer subtype
Just to make this a little more confusing, if you had the statement
x = 2.5
this could be a Currency, Single or Double data subtype. By default, VBScript would consider 2.5 to be
a Double data subtype. In the previous example, the variable x which was assigned a value of 1 could
be a data subtype of Boolean, Byte, Integer or Long. VBScript by default would consider the variable x
with a value of 1 to be an Integer data subtype.
Key Notes:
• The Dim keyword can be used to declare one or more variables. Multiple variables are
separated by comma(s).
• Option Explicit requires all variables to be declared, and is helpful to reduce typing
(spelling) errors
• The value assigned to a variable can be another variable, a named constant (implicit or
explicit) or a literal. A literal is simply static data, and can be a string of text, number,
date or a boolean value. E.g.
a = 2
myStr = “Alarm 1 on”
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