Filter JSON data ( D3.js )

Question

I really need Your help! I have a .JSON file that looks something like this:

{ 
    "_id" : { "$yid" : "279e128r" },
    "userId" : "245981e3",
    "data" : {
        "workRate" : 51,
        "workStages" : [
            { "quantity" : 33, "value" : "APPLES" },
            { "quantity" : 32, "value" : "PEACH" },
            { "quantity" : 12, "value" : "AVOCADO" },
            { "quantity" : 53, "value" : "APPLES" },
            { "quantity" : 22, "value" : "PEACH" },
            { "quantity" : 27, "value" : "AVOCADO" }
        ],
    "timeInterval" : 25,
    "timeSource" : 1
    },
    "sessionStartTime" : 1494311320,
    "sessionEndTime" : 1494336640
}

There are around 500 id ("_id") with 30 participants ("userId").

So I want to take the existing JSON data, and create a new Array that has only 30 Objects ( each object for each participant ) and then find the "data" field and count up the times that vegetables were mentioned, and combine them, and have the number of times that it was mentioned.

{ 
    "userId" : "245981e3",
    "data" : {
        "workRate" : 51,
        "workStages" : [
            { "value" : "APPLES", "times": 2 },
            { "value" : "PEACH", "times": 2 },
            { "value" : "AVOCADO", "times": 2 }
       ]
    }
}
{ 
    "userId" : "7295ew41",
    "data" : {
        "workRate" : 45,
        "workStages" : [
            { "value" : "LEMON", "times": 13 },
            { "value" : "AVOCADO", "times": 42 },
            { "value" : "KIWI", "times": 14 }
       ]
    }
}

I know this sounds difficult, but I believe that there is somebody who will be able to help me out!