An example of validation would be script that requires the user to enter a number within a certain range into a textbox - that is the script demonstrated here. This is called 'client-side validation' since it is done by the user's computer (the client) rather than by the server. For more complex examples of data validation, check the demo on the next page, which also demonstrates the use of the SUBMIT button.

Note that although the above button has the value 'Submit' it is actually a 'normal' push button and not a 'Submit' button. If a Submit button had been used, the example would never see the data to check it—everything would go immediately to the server. Avoiding the Submit button lets you check the data, but it doesn't submit the data to the server. That requires an additional line of code (see further down this page).

The Value property of the text box is used to check the entered value. To get the Value property, the code has to qualify the reference to the name of the text box.

You can always write out the full reference Document.ValidForm.Text1. However, where you have multiple references to form controls, you'll want to do what was done here. First declare a variable. Then use the Set statement to assign the form to the variable TheForm. A regular assignment statement, such as Dim, doesn't work here; you must use Set to preserve the reference to an object.

Using Numeric Values

Notice that the example directly tests the value against a number: it uses the IsNumeric function to make sure the string in the text box is a number. Although VBScript automatically converts strings and numbers, it's always a good practice to test a user-entered value for its data subtype and to use conversion functions as necessary. When doing addition with text box values, convert the values explicitly to numbers because the plus sign (+) operator represents both addition and string concatenation. For example, if Text1 contains "1" and Text2 contains "2", you see the following results:

A = Text1.Value + Text2.Value                             ' A is "12"

A = CDbl(Text1.Value) + CDbl(Text2.Value)          ' A is 3

 

Validating and Passing Data Back to the Server

The simple validation example uses a plain button control. If a Submit control was used, the example would never see the data to check it—everything would go immediately to the server. Avoiding the Submit control lets you check the data, but it doesn't submit the data to the server. That requires an additional line of code (the following code is NOT yet demonstrated on this page, but check back soon...) :

To send the data to the server, the code invokes the Submit method on the form object when the data is correct. From there, the server handles the data just as it otherwise would—except that the data is correct before it gets there. Find complete information about the Submit method and other methods in the Internet Explorer Scripting Object Model documentation, which can be found on the Microsoft® Web site (http://www.microsoft.com/).