VB Script Array Variables

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          VB Script Array Variables




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Arrays are a very useful and easy way of storing variables - and
they're especially easy to use in VBScript. This is due to several
factors:

      VBScript is particularly liberal with any variable definition - that
       means that there is no strict defining of variables to a particular
       data type
      the data type is assigned automatically when the variable is
       loaded with a value
      it's even possible to mix data types within the same array

It is also possible to define the arrays in different ways, for example:

      create the array element by element
      use the VBScript array method
      use the VBScript split method

It's even possible to create multidimensional arrays and to make them
dynamic rather than static.

Creating a Simple VBScript Array

The simplest VBScript array is created by using the dim statement (as
with other variables) however the array also needs to have it's highest
index number defined (the lowest index being 0):

dim name(2)

In this case an array with three elements (0, 1 and 2) has been
defined; and then it's just a matter of assigning values to the
elements:

name(0)="Fred"
name(1)="Jane"
name(2)="Henry"

And then the contents of the array can be used as required:

msgbox name(0) 'Fred

The VBScript Array Method of Creating Arrays

VBScript has its own built in method for creating arrays in bulk rather
than having to do it element by element:



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dim name
name = array("Fred", "Jane", "Henry")
msgbox name(1) 'Jane

The VBScript Split Method of Creating Arrays

VBScript can also create arrays from information such as csv (comma
separated variable) data:

dim name
dim details
details = "Fred,Jane,Henry"
name = split (details, ",")
msgbox name(2) 'Henry

Calculating the Size of Arrays with Ubound

If an array is created using the array method or the split method then
the actual size of the array may not be known; and that's where the
ubound method is useful - this returns the highest index number of the
array:

msgbox ubound(name) '2

The size of the array is, of course, one more than the highest index
number (since the array starts at index number 0).

Multidimensional Arrays

As the amount of information increases (for example storing an age as
well as a name) then the programmer has two choices:

     create multiple arrays - one for each piece of information
     use a multidimensional array where each dimension represents a
      different aspect of the data

The multidimensional array is created in a similar way to the standard
array; for example the following creates a two by three dimension
array (two pieces of information for three people):

dim person(1,2)
person(0,0) = "Fred"
person(0,1) = "Jane"
person(0,2) = "Henry"



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person(1,0) = 21
person(1,1) = 21
person(1,2) = 45
msgbox person(0,1) & " is " & person(1,1) 'Jane is 21

Multidimensional Arrays and Ubound

If the size of a multidimensional array needs to be calculated then the
ubound method can still be used, but this time the dimension number
needs to be included:

msgbox ubound(person, 1) 'The highest index of the first dimension
msgbox ubound(person, 2) 'The highest index of the second dimension

Dynamic Arrays

There is a major disadvantage to arrays - they're static and have a
fixed size; in the above examples three, and only three, elements can
be worked with; if a fourth person (for example) were to be added
then an error would occur. The solution is to use the redim statement
rather than the dim statement:

redim name(0)
name(0) = "Fred"
msgbox (ubound (name)) '0

Now the redim statement can be used to resize the element (the
preserve key word ensures that any existing data is not lost):

redim preserve name(ubound(name) + 1)
name(1) = "Jane"
msgbox (ubound (name)) '1
msgbox name(ubound (name)) 'Jane

Dynamic Multidimensional Arrays

Multidimensional arrays can be dynamic but only one of the
dimensions (the 'right hand' one) can be changed:

redim person(1,0)
person(0,0) = "Fred"
person(1,0) = 21
msgbox (ubound (person, 2)) '0
redim preserve person(ubound (person, 1), ubound (person, 2) + 1)



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person(0,1) = "Jane"
person(1,1) = 21
msgbox (ubound (person, 2)) '1

Summary

Arrays are an easy way to group and store variables in VBScript.
They're created by:

     using dim and the maximum index number of the array
     using the VBScript array method
     using the split method

Arrays can be:

     multidimensional
     dynamic (although only the 'right hand' dimension of a
      multidimensional array can be changed)

Finally the size of any array can be found by using the ubound
method.




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Description: VB Script Array Variables with examples