You can be sure that any user that completes a form will make some data entry mistake, mistakes you want to catch before submitting the data to the database server or other mechanism.

The validation of the data is up to the web programmer. Sometimes you need to make sure that there is a value in a required form field, a valid numerical range, valid characters or a valid format etc.

JavaScript Form Field Validation is used to enhance the user experience by not having the web form submit to the server before validating the user input, this reduces the users’ waiting time and also reduces load on the server.

It should be noted that JavaScript is not to be relied on solely for input validation as the user can turn JavaScript of and bypass the checks.

Why use this framework for Form Field Validation?

Generic form field validation is something that could take months to write, this framework has been written over a period of several years and has been tested on many websites.

Features
- Validates all form fields in one go instead of one at a time
- Checks for required input
- Checks for several (not just one) valid numerical ranges
- Checks for character ranges
- Checks for a valid format
- Checks whether a checkbox, radio button or dropdown selection is made
- Custom error messages
- Define validation scripts with XML
- Define custom error handlers
- Years of development

You can download the validation scripts that we use from here

We’ve just made a JavaScript Form Validation Framework freely available for download. It’s been in use for quite a while now and felt it a good idea to release it to the public for feedback and free use under the GNU license.

You can download the code for free on http://code.google.com/p/javascriptformvalidation/ participation in further development is encouraged.