Problem Twenty

twenty.js

function factorial( n ) {
    var product = bigInt(1);
    for (var i = n; i > 0; i--) {
        product = product.multiply( i );
    }
    return product.toString();
}

var number = factorial( 100 ),
    result = 0;

for (var i = 0; i < number.length; i++) {
    result += parseInt(number[ i ]);
}

document.write( result );