function tctaextend_civicrm_buildForm($formName, &$form) {
if($formName=='CRM_Contribute_Form_Contribution_Main'){
     if($form->_id==2 ){
      CRM_Core_Resources::singleton()->addScriptFile('com.skvare.testextend', 'my_alter_contribform.js');
     }
   }
}

function myextension_civicrm_buildForm($formName, &$form) {
if($formName=='CRM_Event_Form_Registration_Register'){
     if($form->_id==1 ){
      CRM_Core_Resources::singleton()->addScriptFile('com.example.myextension', 'my_alter_eventform.js');
     }
   }
}

if($form->_id==1 ){