To display HTML5 client-side validation error bubbles, use the required attribute.
You do not need to have JavaScript for client side validations like empty text box would never be submitted because HTML5 introduced a new attribute called required which would be used as follows and would insist to have a value:
<!DOCTYPE HTML> <html> <body> <form action = "/cgi-bin/html5.cgi" method = "get"> Enter email : <input type = "text" name = "newinput" required/> <p>Try to submit using Submit button</p> <input type = "submit" value = "submit" /> </form> </body> </html>