The purpose of introducing HTML5 validation is to notify a user that a page contains some mandatory information that needs to be filled or corrects the users for any errors using the browser's built-in processing. We should take advantage of all the capabilities and knowledge that the browser has, to catch errors within a form, before sending it to the server. Also, we need not bother about the time and expense of a network round-trip or getting a response from the server about some stupid error.
<input> attributes such as
pattern used in combination with CSS pseudo-class selectors make it easier to write the checks and display feedback to the user. There are also other advanced validation techniques that ...