HackerRank Missing Numbers

missing_numbers.js

// Complete the missingNumbers function below.
function missingNumbers(arr, brr) {
    var arrCt = {};
    var brrCt = {};
    var missing = [];
    var curr;
    //10
    //203 204 205 206 207 208 203 204 205 206
    //13
    //203 204 204 205 206 207 205 208 203 206 205 206 204

    //create brr hash with counts
    for (var i = 0; i < brr.length; i++) {
        curr = brr[i]
        if (brrCt[curr]) {
            //if entry exists, increment value counter
            brrCt[curr] += 1;
        } else {
            //if no entry exists, start counter at 1
            brrCt[curr] = 1;
        }
    }

    //create arr hash with counts
    for (var j = 0; j < arr.length; j++) {
        curr = arr[j]
        if (arrCt[curr]) {
            //if entry exists, increment value counter
            arrCt[curr] += 1;
        } else {
            //if no entry exists, start counter at 1
            arrCt[curr] = 1;
        }
    }

    //iterate the brr hash 
    for (const [key, value] of Object.entries(brrCt)) {
        //if doesn't exist in arr or count is different add to missing
        if((key in arrCt) && (arrCt[key] == brrCt[key])) {
            //skip
        } else {
            missing.push(key);
        }

    }
    return missing;
}