Input, validation, testing.
So if you open an application that contains a registration form.
And you may notice a certain amount of feedback about incorrect data or maybe incorrect data format
that you entered.
Such as this field is required, you can't leave this field blank.
Or whatever it will be.
This is called form validation.
It helps both the owner and the users of the application to ensure that they're filling out the forms
correctly.
Right.
The target web application can check the length in the format of the form fields when you enter data.
That's how it works.
So if the energy information is correct, the application allows the data to be submitted to the server.
And if it's not, then it gives you an error message explaining what needs to be corrected.
So basically, there are a few reasons to implement form validation, and of course, one of them is
to help the application to work and store data properly.
But there is also another important reason, and that is the security of the application and users.
There are many ways that malicious users or a pen tester can misuse these forms to damage the application.
And almost all major Web attacks, such as escarole injection access, they're all caused by improper
data validation.
So there are two approaches, a form validation, client side and server side validation, and as the
name suggests, in a client side validation, the data is validated in the browser before being submitted
to the server.
So by using JavaScript or HTML five's built in validation, navigation can easily implement data validation
in the client.
Client side validation is quick and easy, and it's more user friendly when it's implemented.
But for security reasons, it's not really a barrier.
So server side validation comes in pretty handy.
And as that name suggests, the validation occurs in the server after the data submitted.
So it doesn't provide errors until the entire form has been submitted, so it's a last line of defense
against incorrect or malicious data.
Now, in the real world, developers tend to use a combination of client side and server side validation.
And there's a popular saying about this situation.
Never trust data pass to your server from the client.
That means if the provided information is not 100 percent correct, then it is all incorrect.