Now we will see how we can validate our entered form data before submitting it to the web server.The following example shows how to validate an entered email address.
Also, the ‘@’ must not be the first character of the email address, and the last dot must at least be one character after the ‘@’ sign. Most often, the purpose of data validation is to ensure correct input to a computer application.Validation can be defined by many different methods, and deployed in many different ways.Server side validation is performed by a web server, after input has been sent to the server.All warnings except "option explicit" are enabled in this online edition, although certain warnings are displayed only once.For full control over which warnings are displayed, download the Java Script Lint software.
Form validation normally used to occur at the server, after the client had entered all the necessary data and then pressed the 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 the client and request that the form be resubmitted with correct information.
This was really a lengthy process which used to put a lot of burden on the server.
Java Script provides a way to validate form's data on the client's computer before sending it to the web server. First let us see how to do a basic form validation.
In the above form, we are calling validate() to validate data when onsubmit event is occurring.
The following code shows the implementation of this validate() function.