Javascript Function

The setup and validation of radio buttons appears to be the form field that gives many webmasters the most difficulty in setting up. In actual fact the setup of these fields is the most simple of...

Validation of dropdown lists is fairly simple. Since the only possible values that the list can have are the ones that you code into the list, the only invalid values will be ones that you know...

When you have text fields on your form (or drop down lists that include invalid values) it can make sense to validate the field immediately after the field has been updated rather than waiting un...

When you include a form on one of your web pages, there will usually be one or more fields where you wish to perform some sort of validation before allowing the form to be submitted. This validat...

Just because you have validated all of the individual fields on your form doesn't mean that you have finished validating the form. You know by this point in your validation that what has been...

The simplest field validation is to test a text input field to see if something has been entered into it. All that you need to do is to compare the field with an empty string like this: ...

Javascript does not contain functions that test specifically for alphabetic or numeric content but we can easily provide these functions for ourselves. Just add the following code into the head s...

It is all very well validating that a field only contains certain characters but there will be times when you need to test that a specific character appears a set number of times as well. Example...

Some times certain characters are only valid when they appear next to certain other characters. Other times certain characters are valid only when they don't appear next to certain other char...

When you have certain characters that you only want in your input field in set combinations with certain other characters then the testing becomes slightly more complicated than just testing for ...