Reply To: Registration Form Validation

From Dokan demo
which the main plugin of my website
URL : http://dokandemo.wedevs.com/my-account/
I do not know why it does not act like this demo
In my website If someone does not fill the email field and then click on RIGISTER button it will submit the form and then show error message!! why there is no javascript that prevent this behaviour, it should check all required fields before submission