div id with same name before the original div

Good morning, I have a question how do I get an id of div. One more after the initial div.

EX:

  <div class="1">
      <div class="2">
         <div class="3">
            <div class="4">
               <div class="up" id="2"> UP </ div> <<- get id here
            </ div>
         </ div>
      </ div>
    </ div>

  <div class="1">
      <div class="2">
         <div class="3">
            <div class="4">
               <div class="up" i开发者_如何学编程d="1"> UP </ div> <<- Click
            </ div>
         </ div>
      </ div>
    </ div>

I'll be grateful for the help.

Assuming the outer div always has the same class:

$('.up').click(function(){
   alert( $(this).closest('.1').prev().find('.up').attr('id') );
});

        function getId(){
           var allDiv = document.getElementsByTagNames("div");
           for(i=0; i<allDiv.lebgth; i++){
                 for(j=i; j<allDiv.lebgth; j++){
                      if(allDiv[i].className == allDiv[j].className )
                              return allDiv[i].getAttribute("id");
                       }
                  }
                  return "";
        }