Example: attribute, so you can test those by trying to submit any of the forms without entering anything in the field.
Browser support for form validation features is pretty strong, and you can easily polyfill them where necessary.
They are often used to perform complex search-and-replace operations, and to ensure that text data is well-formed.
This is a Boolean attribute used to indicate that a given input field’s value is required in order to submit the form.
In the past, client-side validation could only be achieved using Java Script or using libraries from frameworks (think j Query validation plugin).
But that is changing or rather has changed because validation can now be done using HTML5 without having to write complex Java Script validation code.
For example, in an email form field, instead of entering a valid email address, the user might enter an invalid one or malicious data obviously ignoring the intent of the request.
When it comes to validating form values, it can be done on the client-side (web browser) and on the server-side (using your preferred server-side language).