用jq把span的值实时改变input的val值

jq两个及以上加减选框

把增减span的值传入input

同级下确定最后的input

$(this).parent('.number').children("input").last().val(mm);

//html
  <form method="post" action="__APP__/default/fill_info.html">
    <div class="ticket_species_3">
      <span class="ticket">儿童价</span>
      <div class="number">
        <input type="button" value="-" class="jian" />
        <span>1</span>
        <input type="button" value="+" class="jia" />
        <input type="hidden" name="et" value="1" class="et">
      </div>
      <span class="price">￥50</span>
    </div>
    <div class="ticket_species_3">
      <span class="ticket">成人价</span>
      <div class="number">
        <input type="button" value="-" class="jian zj" />
        <span class="cr_num">1</span>
        <input type="button" value="+" class="jia zj" />
        <input type="hidden" name="cr" value="1" class="cr">

      </div>
      <span class="price">￥100</span>
    </div>

    <div class="ticket_species_4">
      <input type="reset"  value="取消" class="qxbtn">
      <input type="submit"  value="确定" class="surebtn" >
    </div>
  </form>


//jq
      $(".ticket_species_3 .number .jian").on("click",function(){
        var mm = parseInt($(this).next("span").text());
        if(mm >0){
          var mm = mm-1;
          $(this).next("span").text(mm);
          $(this).parent('.number').children("input").last().val(mm);
        }else{
          $(this).next("span").text("0");
          $(this).parent('.number').children("input").last().val('0');
        }
      })

      $(".ticket_species_3 .number .jia").on("click",function(){
        var mm = parseInt($(this).prev("span").text());
          var mm = mm+1;
          $(this).prev("span").text(mm);
          $(this).parent('.number').children("input").last().val(mm);
      })