向各位请教下javascript内存泄露leak的原因有哪些?

     LTEvent.addListener(this.map,"mouseup",function(point, button)

         {

         if(button==2)

         { //只对鼠标右键其效果

         var latlng=other.map.getClickLatLng(point); //像素坐标转经纬度

         var m_Lat=latlng.getLatitude();

         var m_Lng=latlng.getLongitude();

         var addMarkTip=document.getElementById("addMark");

         addMarkTip.style.display='block';

         addMarkTip.style.zIndex='9999';

         var m_Address='';

		 var subAdd=BGMmap.$('addsubmit');

		 var SubCancelBtn=BGMmap.$('SubCancel');

		 var Addrobj=BGMmap.$('addrid');

		 SubCancelBtn.onclick=function() //取消按钮

         {  

                 addMarkTip.style.display='none';

                 addMarkTip.style.zIndex='2000';

                 Addrobj.value=''; 

         };

         addMarkTip=null;

         SubCancelBtn=null;

         subAdd.onclick=function()

          {

           

             m_Address=Addrobj.value;

             window.external.AddMarkerToMap(m_Lat,m_Lng,m_Address,1); //添加到数据库之后自动关闭

             addMarkTip.style.display='none';

             addMarkTip.style.zIndex='2000';

             Addrobj.value='';  //清空文本框

             

             

        

             //添加标注

             var m_marker =new LTMarker(latlng);

             other.map.addOverLay(m_marker);

             m_marker.setLabel(m_Address);

             

             var tmp_marker=m_marker;

             subAdd=null;

             LTEvent.addListener(m_marker, "click" , function(pnt,btn){ //点击标注提示更新、删除

             

             

                 if(btn==1) {//只能左键点击

                 var m_Lat1=m_Lat;

                 var m_Lng1=m_Lng;

                 

                

                 

                 //显示更新删除对话框

                 var DeleteUpdate=document.getElementById("DeleteUpdate");

                 DeleteUpdate.style.display='block';

                 DeleteUpdate.style.zIndex='1000';

                 var subUpdate=BGMmap.$('updatesubmit');//获取更新提交按钮

                 var updaterobj=BGMmap.$('addridupdate'); //获取更新输入框

                 updaterobj.value=m_Address; //填充更新文本框

                 //点击更新

                  subUpdate.onclick=function() 

                    {

                       var m_updateAddress=''; //更新地址

                        m_updateAddress=updaterobj.value;

                        m_Address=updaterobj.value;

                        tmp_marker.setLabel(m_Address);

                        window.external.UpdateMarkerToMap(m_Lat1,m_Lng1,m_updateAddress,1); //更新到服务端

                        DeleteUpdate.style.display='none';

                        DeleteUpdate.style.zIndex='1000';

                        tmp_address=new LTMarker(latlng);

                   };

                   subUpdate=null;

                   var otherobj=other;

                   

                   //删除按钮

                   var subDelete=BGMmap.$('deletesubmit');

                   subDelete.onclick=function()

                   {

                        window.external.DeleteMarkerToMap(m_Lat1,m_Lng1,1); //删除提交到服务端

                        DeleteUpdate.style.display='none';

                        DeleteUpdate.style.zIndex='1000';

                        otherobj.map.removeOverLay(tmp_marker); //删除标注

                    };

                    subDelete=null;

                   //点击取消

                  var  UDCancelbtn=BGMmap.$('UDCancel');

                  UDCancelbtn.onclick=function()

                  {

                     DeleteUpdate.style.display='none';

                     DeleteUpdate.style.zIndex='1000';

                  };

                  UDCancelbtn=null;

                  DeleteUpdate=null;

                  }

               });

        }; subAdd=null;

        }

       

    });