JSFiddle - React, Tailwind, and code Playground

CSS

div {
    margin: 0;
    padding: 2px;
    border-bottom: 1px solid black;
}

JavaScript

var ResultSet = {

      Result:[
        {
            "file_size":"722694",
            "desc":"description1"
        },

        {
            "file_size":"19754932",
            "desc":"description1"
        },

        {
            "file_size":"778174",
            "desc":"description2"
        },

        {
            "file_size":"244569996",
            "desc":"description1"
        },

        {
            "file_size":"466918",
            "desc":"description2"
        }
      ]

    };

    var data = {};
    var array = ResultSet.Result;

    var i = 0;
    var currentDesc, currentSize;
    var sizeDiv;
    var sumItem;

    //Sum the sizes for each description
    for(i = 0; i < array.length; i++) {
        currentDesc = array[i]["desc"];
        currentSize = parseInt(array[i]["file_size"], 10);
        
        data[currentDesc] = typeof data[currentDesc] === "undefined" ? currentSize : data[currentDesc] + currentSize;
    }

    //Print the summations to divs on the page
    for(sumItem in data) {
        if(data.hasOwnProperty(sumItem)) {
            sizeDiv = document.createElement("div");
            sizeDiv.innerHTML = sumItem + ": " + data[sumItem].toString();
            document.body.appendChild(sizeDiv);
        }
    }