Edit JSON Fields [closed]

Answer 1

 var source={
                "XXXX": {
                    "type": "RSS",
                    "value": ""
                },
                "YYYY": {
                    "type": "String",
                    "value": ""
                },
                "ZZZZ": {
                    "type": "String",
                    "value": ""
                }
            }

And element you wanted to add

 var element={
        "type": "Image",
        "value": "a7e8bec0-87ed-11e2-aa2e-52540025ab96_2_1362746556"
    };

You can do with below script,

source["MMMM"]=element;

or

source.MMMM=element;