remove null values from json - Mailing list pgsql-sql

From Michael Moore
Subject remove null values from json
Date
Msg-id CACpWLjMXYaOJ+qDGX4xAduhWTHt0F62K2e2sDazH7tG_m9Qnpg@mail.gmail.com
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Responses Re: remove null values from json  (Pavel Stehule <pavel.stehule@gmail.com>)
List pgsql-sql
This is ALMOST what I want:
select json_strip_nulls ('[{ "f1":1 , "f2":null  , "f3":"NULL" , "f4":""  }]');
the result is:
"[{"f1":1,"f3":"NULL","f4":""}]"

As you can see, the "f2" object has been removed. I would also like to remove the f3 and f4 objects. 

I realize I won't be able to use the json_strip_nulls function to do this. I could brute force it by doing "json to array" then looping through the array and picking only the objects I want, and then using the chosen objects to build an new JSON document. 

I suspect there is a more elegant way to accomplish the same objective.
Ideas?

PS. It would be great to have a json_strip_values (json, array) where array contains the list of values you want removed. 

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