Default print format JS for v15 no longer

1

The following JS that used to work in earlier versions (<15) now does not work. I would appreciate if any suggestions:

frappe.ui.form.on('Purchase Order', {
    refresh(frm) {
        if (cur_frm.doc.grand_total> 5000) 
		{
			
			frm.meta.default_print_format = "ApprovalTemplate";
     
        }
    }
});