ASP Tutorials - Herong's Tutorial Notes
Dr. Herong Yang, Version 4.11

Visual Basic Script (VBScript)

Part:   1  2  3 

ASP Tutorials - Herong's Tutorial Notes © Dr. Herong Yang

hyBook - Guestbook Application

Using MS Access Databases

ActiveX Data Object (ADO)

Controlling Response Header Lines

Microsoft Scripting Runtime DLL

Using Cookies

ASP Sessions

ASP Objects

Microsoft Script Debugger

Internet Information Services (IIS)

... Table of Contents

(Continued from previous part...)

Arrays

Array is a build-in data structure in Visual Basic language. It can used to store a collection of data elements with indexes to access each element. Arrays can be declared to hold a fixed number of elements as: 

dim weekdays(5)

Arrays can also be declared to a variable number of elements as: 

dim weekdays()
redim weekdays(5)
other statements
redim preserve weekdays(7)

Elements in a array can be iterated with the "for each ... next" statement as: 

dim weekdays(5)
other statements
for each day in weekdays
   other statements
next

Here is a simple ASP page to how the features of arrays: 

<script language="vbscript" runat="server">
'  array.asp
'  Copyright (c) 2002 by Dr. Herong Yang
'  This program demonstrates some special rules about arrays.
'
   response.write("<html><body>")
   response.write("<b>Tests on arrays</b>:<br/>")
   dim days()
   redim days(5)
   ' Referring elements by index
   days(0) = "Mon"
   days(1) = "Tue"
   days(2) = "Wed"
   days(3) = "Thu"
   days(4) = "Fri"
   ' Iterating through indexes
   for i=0 to 5-1
      response.write("Element " & i+1 & " = " & days(i) & "<br/>")
   next
   ' Increasing the size of the array
   redim preserve days(7)
   days(5) = "Sat"
   days(6) = "Sun"
   i = 1
   response.write("Two days added:<br/>")
   for each d in days
      response.write("Element " & i & " = " & d & "<br/>")
      i = i + 1
   next
   response.write("</body></html>")
</script>

Output 

Tests on arrays:
Element 1 = Mon
Element 2 = Tue
Element 3 = Wed
Element 4 = Thu
Element 5 = Fri
Two days added:
Element 1 = Mon
Element 2 = Tue
Element 3 = Wed
Element 4 = Thu
Element 5 = Fri
Element 6 = Sat
Element 7 = Sun
Element 8 =

Note that:

  • Indexes of elements in arrays starts with 0.
  • "redim" can only be used against arrays that are declared with dynamic size.
  • "redim" can be used repeatedly.
  • "redim preserve" can be used to preserve the elements that already exist.
  • "for each ... next" statement revealed an extra element in the array. I am not sure why?

"Collection" Class

Collection: A class representing a collection of ordered elements. The stored elements can be referred by an index number or by the key associated with the elements. It offers the following methods and properties based on the documentation of Visual Basic .NET:

  • "Item(i|key)": Property to return the element of the specified index or key. Item() is the default method of a collection object, so you can call this method without the method name, like object(i|key), instead of object.Item(i|key).
  • "Count": Property to return the number of elements in the collection.
  • "Add(element)": Method to add an element at the end of the collection without a key.
  • "Add(element, key)": Method to add an element at the end of the collection with a key.
  • "Remove(i|key)": Method to remove the element of the specified index or key.

Unfortunately, I was not able to write an ASP page with a new collection object.

Part:   1  2  3 

Dr. Herong Yang, updated in 2003
ASP Tutorials - Herong's Tutorial Notes - Visual Basic Script (VBScript)