How to open select element using jquery

Answer 1

$(document).ready(function(){  
  $('#selId').on('click',function(){
     //do stuff here
  });
  $('#selId').trigger('click');
});

This should work.

Update:

$(document).ready(function(){  
  $('#selId').click(function(){
     //do stuff here
  });
  $('#selId').click();
});

Very similar to the other answer, but that should do it also rather then "click" you can try "focus"