Bootstrap input validation?

Question

css

Tell me, where is the email validation function implemented in bootstrap?
For example, here is a site, http://bootstrap-4.ru/docs/4.0/components/forms/ .

When you click the submit button, a pop-up window appears as in the screenshot. Where is it implemented?
I want to do this for phone number and name.
ps I know about validation in php and js, but I want to do exactly the same and find out how it is implemented here.

Answer 1

<input type="email">
During the submission, by default it checks (and displays a message) if the soap (#@#.#) is incorrectly entered and characters are entered.