reduceRight (JavaScript Array Method)

const tnwNum = [20, 9, 20, 8, 100];

function tnwFun1(){
    document.getElementById("demo").innerHTML = tnwNum.join(", ");
}

function tnwFun2(){
    var result = tnwNum.reduceRight(tnwFun3);
    document.getElementById("demo").innerHTML = result;
}

function tnwFun3(numRight, sum){
    return numRight - sum;
}