Clever way to order a json item by key in postgresql (two examples)

I need to sort a json item in a record, so here are two examples: # First case

create table jsontable (
    jsonitem json
);

Next I insert a json item:

insert into jsontable(jsonitem) values ('{ "3" : "foo", "2" : "bar", "1" : "qux" }');

Then I query the values:

select t.jsonitem from jsontable t;
                 jsonitem                  
-------------------------------------------
 { "3" : "foo", "2" : "bar", "1" : "qux" }
(1 row)

Let's suppose the key is unique and is an integer > 0; **Question 1:** ¿ How to sort the json item values by the key value, and get the following ?

{ "1" : "qux", "2" : "bar", "3" : "foo" }

# Second case This case use named keys and named values.

create table jsontable_arr(
   jsonitem json
   );

insert into jsontable_arr(jsonitem) values ('[  { "key" : "3" , "value": "foo"}, { "key" : "2" , "value": "bar"}, { "key" : "1" , "value": "qux"} ]');

select t.* from jsontable_arr t;
                                                jsonitem
--------------------------------------------------------------------------------------------------------
 [  { "key" : "3" , "value": "foo"}, { "key" : "2" , "value": "bar"}, { "key" : "1" , "value": "qux"} ]
(1 row)

**Question 2:** ¿ How to sort the json array item by the key value, and get the following?

[  { "key" : "1" , "value": "qux"}, { "key" : "2" , "value": "bar"}, {"key" : "3" , "value": "foo"} ]

Thanks for your suggestions.