Form Validation Options
The steps involved in transmitting form data from the client to the Web server
User loads web form.
User enters data in to web form fields
User clicks submit
On submit page validates fields using JavaScript. If validation errors are found then the validation script stops the browser from canceling posting the data to the web server and displays error messages as needed.
If the form passes the data validation process then the browser will URL encode the values of every field and post it to the server.
The server reads the posted data from the query string and then again validates the data just to ensure data consistency and to prevent any non-validated data because JavaScript was turned off on the clients browser from being inserted in to a database or passed on to other process.
If the data passes the second validation check then the server side code will continue with the requested processes.
In my opinion, it is mandatory to validate data using client side and server side validation as a fail over process. The client side validation allows users to correct any error before they are sent to the web server for processing, and this allows for an immediate response back to the user regarding data that is not correct or in the proper format that is desired. In addition, this prevents unnecessary interaction between the user and the web server and will free up the server over time compared to doing only server side validation. Server validation is the last line of defense when it comes to validation because you can check to ensure the user’s data is correct before it is used in a business process or stored to a database.
Honestly, I cannot foresee a scenario where I would only want to use one form of validation over another especially with the current cost of creating and maintaining data. In my opinion, the redundant validation is well worth the overhead.
