Story05Js :: "history book counter"

function visitedSum(book,page){
    var sum = 0;
    Object.keys(historybook[book]).forEach(page => {
        sum += historybook[book][page];
    });
    return sum;
}

function visitedCount(book,page){
    var count = 0;
    Object.keys(historybook[book]).forEach(page => {
        if ( historybook[book][page] > 0 ) {
            count += 1;
        }
    });
    return count;
}