HTML5 Typography - Learn HTML5 by Creating Fun Games - page 86

an attractive feature designed to save time and effort, we'll focus on the functionality
that can best help us with respect to this auto validation.
Custom validation
One of the properties of ValidState is the Boolean customError , which specifies
whether a custom error message has been set to the field element or if the browser
is to display a generic error message for this element in case the form does not valid-
ate. To set a custom error message, we can call the setCustomValidity() meth-
od of the form element itself and assign a message for the browser to use when
needed, as follows:
var email = document.querySelector("#myForm
input[type='email']");
email.pattern = "\\w{3,}@packtpub\\.com";
email.setCustomValidity("Please enter a valid
Packt email address...");