对象数组 深拷贝

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;  }