The idea behind Java Script form validation is to provide a method to check the user entered information before they can even submit it.Java Script also lets you display helpful alerts to inform the user what information they have entered incorrectly and how they can fix it.
The following example shows how you can validate an email address for a form.
Date Validation Email Validation Phone Number Validation U.
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.
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.
An email address must contain at least a ‘@’ sign and a dot (.).