如何在Javascript中读取值或反序列化JSON结构？

Question

from an associative and multidimensional Array in PHP i get this object by json_encode():

{"2047":
  {"f1a":
   {"val":["7","7","6","1","6","6"],
    "cnt":6,
    "sum":33,
    "avg":5.5
   },
  {"f2a":
   {"val":["7","6","5","7","5","3","5","7","6","7"],
    "cnt":10,
    "sum":58,
    "avg":5.8
   },
  "2048": ...
}

and i want to read the value of avg of f2a and 2047.