VBScript Reference Manual for InduSoft Web Studio

InduSoft Web Studio VBScript Reference Manual
While VBScript string handling capability can be very useful, programmers should be aware of
information given in Microsoft Knowledge Base Article 170964 1 . This article states that when strings get
very large (e.g. 50kB or larger), the time to concatenate these strings can be very long. For example, a
typical string concatenation where:
Dim dest, source ‘ String variables
Dim i, N
For i = 1 to N
dest = dest & source
Next N
Using the programming method above, the Article notes that the length of time to perform the
concatenation increase proportionately to N-squared. This increase in time is due to the method
VBScript uses to concatenate strings, which is:
• allocate temporary memory large enough to hold the result.
• copy the dest string to the start of the temporary area.
• copy the source string to the end of the temporary area.
• de-allocate the old copy of dest.
• allocate memory for dest large enough to hold the result.
• copy the temporary data to dest.
The Article details a method using the Mid$ statement and pre-allocation of memory to significantly
reduce the time to concatenate large strings. Also, you can reference the section on Classes for
another method to speed string concatenation.
There are several functions available to manipulate strings. Refer to the reference material in the
Appendix for a detail description of these functions.
String Functions
Function Description
InStr Returns the position of the first occurrence of one string within another. The search begins at the
first character of the string
InStrRev Returns the position of the first occurrence of one string within another. The search begins at the
last character of the string
LCase Converts a specified string to lowercase
Left Returns a specified number of characters from the left side of a string
Len Returns the number of characters in a string
LTrim Removes spaces on the left side of a string
Mid Returns a specified number of characters from a string
Replace Replaces a specified part of a string with another string a specified number of times
Right Returns a specified number of characters from the right side of a string
RTrim Removes spaces on the right side of a string
Space Returns a string that consists of a specified number of spaces
StrComp Compares two strings and returns a value that represents the result of the comparison
String Returns a string that contains a repeating character of a specified length
StrReverse Reverses a string
Trim Removes spaces on both the left and the right side of a string
UCase Converts a specified string to uppercase
1 See http://support.microsoft.com/kb/q170964/
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