[jquery] how to call a function from another function in Jquery

<script>
  $(document).ready(function(){
    //Load City by State
    $('#billing_state_id').live('change', function() {
       //do something
    });   
    $('#click_me').live('click', function() {
       //do something
       //need to recall $('#billing_state_id').live('change', function() { but how?
    });   
  });
</script>

Load City by State working fine but i don't know whether it's possible or not to call it within another function like $('#click_me').live('click', function().

wrap you shared code into another function:

<script>
  function myFun () {
      //do something
  }

  $(document).ready(function(){
    //Load City by State
    $(document).on('change', '#billing_state_id', function() {
       myFun ();
    });   
    $(document).on('click', '#click_me', function() {
       //do something
       myFun();
    });   
  });
</script>

I think in this case you want something like this:

$(window).resize(resize=function resize(){ some code...}

Now u can call resize() within some other nested functions:

$(window).scroll(function(){ resize();}