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 splitmethod
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):
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:
And then the contents of the array can be used as required:
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:
The VBScript Split Method of Creating Arrays
VBScript can also create arrays from information such as csv (comma separated variable) data:
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:
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):
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:
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:
Now the redim statement can be used to resize the element (the preserve key word ensures that any existing data is not lost):
Dynamic Multidimensional Arrays
Multidimensional arrays can be dynamic but only one of the dimensions (the 'right hand' one) can be changed:
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.
Mark Alexander Bain - Mark Alexander Bain is a writer, Mo Bro and consultant for all aspects of software development at dsquared. He has also written regularly ...
