Match A JSON Value to A Key Or Keys

Match A JSON Value to A Key Or Keys

Suppose I have a json object  as seen below:

  2.  { "testTypeA":"A",  "testTypeB":"B",  "testTypeC":"C", "assortedTest":["X","D","C"] }

I have seen many jQuery tutorials on getting json values by using the key but I have not seen any tutorials on getting the key if the value is known. 

In the above json object, if I would like to get all the keys that have a value of C, what method could I use?