_form.html.erb

<%= form_for @foo do |f| %>
<%= f.text_field :name %>
<%= f.text_field :color %>
<%= f.submit 'Save' %>
<%= f.email_field :friend %>
<%= f.submit 'Semd to a friend', formaction: params.merge(action: 'send_to_friend') %>
<%- end -%>
<script type="text/javascript">
if(! ('formAction' in document.createElement('input') ){
  document.addEventListener('click', function(evt){
    var action = evt.target.getAttribute('formaction');
    if(action && evt.target.form){
      evt.target.form.action = action;
    }
  });
}
</script>