function clone(obj) {

     var o;

     if (typeof obj == "object") {

         if (obj === null) {

             o = null;

         } else {

             if (obj instanceof Array) {

                 o = [];

                 for (var i = 0, len = obj.length; i < len; i++) {

                     o.push(clone(obj[i]));

                 }

             } else {

                 o = {};

                 for (var j in obj) {

                     o[j] = clone(obj[j]);

                 }

             }

         }

     } else {

         o = obj;

     }

     return o;

 }