var abc=[
{
id:1,
         url:""
         sub:[
           {
             id:1001,
             url:"a0001.htm",
             sub:0
           },
           {
             id:1002,
             url:"a0002.htm",
             sub:0
           }
         ]
},
{
        id:2,
       url:""
       sub:[
         {
           id:1003,
          url:"",
          sub:[
              {
               id:1005,
              url:"a10005.htm",
              sub:0
              },
               {
                id:1006,
               url:"a10006.htm",
               sub:0
               }
             ]
         },
         {
           id:1004,
           url:"a0004.htm"
           sub:0
         }
       ]
}
];请问如何将以上这个json结构实现为树型目录,烦请高手帮忙(主要是我用递归老是不对)。