JSFiddle - React, Tailwind, and code Playground

HTML

<p id="results"></p>

JavaScript

var dataArray = {
    "dribbble":{
        "username":"JeremDsgn",
        "followers":242,
        "diff":{
            "data":[230, 231, 236, 238, 239, 239, 242]
        }
    },
    "twitter":{
        "username":"jeremdsgn",
        "followers":"592",
        "diff":{
            "data":[576, 578, 578, 581, 584, 589, 592]
        }
    },
    "behance":{
        "username":"JeremDsgn",
        "followers":17,
        "diff":{
            "data":[16, 15, 15, 16, 16, 16, 17]
        }
    }
};

var total = [0,0,0,0,0,0,0];

for (var site in dataArray) {
    for (var i = 0; i < dataArray[site].diff.data.length; i++) {
        total[i] += parseInt(dataArray[site].diff.data[i], 10);
    }
}

$.each(total, function(i, v){
    $('#results').append(v + ", ");
});

console.log(total) // [822, 824, 829, 835, 839, 844, 851]