jquery - Using Javascript in Ruby on Rails -

i have drop-down list can select person.

<%= select_tag "person", options_from_collection_for_select(person.all, :id, :name, 1) %> 

when person selected want display persons phone number. how can that?

after looking @ lot of solutions of how use javascript/jquery/coffeescript in ror i´m bit confused on place in files , use. can please give me simple example?

pass changed person id javascript function on onchange event.

---

<%= select_tag "person", options_from_collection_for_select(person.all, :id, :name, 1) ,  :onchange => "your_js_function_to_display_phone_for(this.value)"%> 

trigger ajax request , return phone number database. ( can client side if person list small )

---

<script type="text/javascript">  function your_js_function_to_display_phone_for(person_id) {  // given person_id  // assuming route return me phone number   new ajax.request('/person/get_phone_number/'+person_id, {asynchronous:true, evalscripts:true, method:'post',  onsuccess:function(request) {     // modify place whether update on particular div_id      // or appropriate action returned request.body       alert("phone number person is: "+request.body); },  parameters:form.serialize(this)}); }  </script> 

edit:

your controller should this.

class personcontroller     def get_phone_number         person = person.find(params[:id])         phone_number = person.get_phone_number          render :text => phone_number      end  end