Button For User Details

How can i write a script for a button which i have inserted in a doctype …After clicking the button i want to fill the details of the below fields with the current user …
The fields are User fullname, User Email,Uer mobile no…
Hope You will Help me…

Try frappe.msgprint

After clicking the verify button i want to fill the fields below …can u help me with the code…

And i also tried the following and the website stops working when i tried to implement the second form and if i comments and its working ,if anything wrong with my code please let me know …
frappe.ui.form.on(‘Registration’, {
refresh: function(frm) {
frm.add_custom_button(__(‘Get user Email Address’),function(){
}, __(“User Mail”));
callback:function(r) { };