Display pattern error without submitting the form

i have a form that i have put on couple pages, I have a 'Next' button wich is displaying the next page, and, when on last page turns to a submit button But I want my form to display the pattern errors of my text input before going to nextpage. So how can I trigger this message with javascript ? I prefer not using JQuery, but if there is no other solution i'll take it :)

This is the pattern/empty-field error i'm talking about

Thank you for your help !