Introduction

Form validation normally used to occur at server end after client had entered all necessary data and then pressed Submit button. If the data entered by a client was incorrect or was simply missing, the server would have to send all the data back to client and request that form to be resubmitted with correct information. This was really a lengthy process which used to put a lot of burden on server.

JavaScript provides a way to validate form's data on the client's computer before sending it to the web server.