Adding properties to existing JSON object with PLV8   

ujson_add_prop function: Add/Update properties of a JSON object

I used PL/V8 1.4.3, binaries for windows users here. I settled on taking json and outputting json from this function instead of jsonb, because when I tried to swap out json with jsonb, I got back the same json object as what I put in. Not sure why.

So here is the function

CREATE OR REPLACE FUNCTION ujson_add_prop(param_o json, 
        param_key text, param_value anyelement) 
    RETURNS json AS $$
    var result = param_o;
    result[param_key] = param_value;
    return (result)
$$ LANGUAGE plv8 IMMUTABLE STRICT;

Taking the function for a test drive

-- just tack on taker name 
SELECT ujson_add_prop(e_form::json, 
    'Taker Name', first_name || ' ' || last_name)::jsonb
FROM survey;

Which outputs

           ujson_add_prop
-------------------------------------------------------------------------------
 {"qa": [{"Favorite Color": "red"}, {"Significant Other": "Minnie"}], 
 "Taker Name": "Micky Mouse"}
 {"qa": [{"Favorite Color": "white"}, {"Significant Other": "Mick"}], 
 "Taker Name": "Minnie Mouse"}
(2 rows)

-- since it's defined as anyelement you can do this too
SELECT ujson_add_prop(e_form::json, 'Header', h)
FROM survey , LATERAL (SELECT id, first_name,last_name) As h;

Which outputs:

    ujson_add_prop
-----------------------------------------------------------------------------
 {"qa":[{"Favorite Color":"red"},{"Significant Other":"Minnie"}],
 "Header":{"id": 1,"first_name":"Micky","last_name":"Mouse"}}
 {"qa":[{"Favorite Color":"white"},{"Significant Other":"Mick"}],
 "Header":{"id": 2,"first_name":"Minnie","last_name":"Mouse"}}

The function also doubles as a setter. If I had for example a key already defined called "Header" in root of my JSON object, it would replace the old value with the new value.

On a side-note, I also discovered that my other tried and true friend hstore is a great companion to JSON allowing me to easily remorph JSON arrays such as survey questions into key-value for easier querying. More on that later.