IF statements - How to reduce / simplify the amount of source code

Question

I'm in trouble trying to reduce this section of code of my function:

checkData(day, month, year, area)
{
    if(area == "year" && year == this.year)
        return true;

    if(area == "month" && month == this.div && year == this.year)
        return true;

    if(area == "day" && day == this.day && month == this.div && year == this.year)
        return true;

    return false;
}

How could I simplify/reduce the amount of source code for these IF clauses?

Answer 1

Your if clauses can be rewritten to:

checkData(day, month, year, area)
{
    if(year == this.year) {
        if(area == "year") return true;
        if(month == this.div) {
            if(area == "month") return true;
            if(day == this.day) {
                if(area == "day") return true;
                return false;
            }
        }
    }
}

And then to:

checkData(day, month, year, area)
{
    if(year != this.year) return false;
    if(area == "year") return true;
    if(month != this.div) return false;
    if(area == "month") return true;
    if(day != this.day) return false;
    return area == "day";
}

Another possible syntax, depending on the programming language (e.g. C++):

checkData(day, month, year, area)
{
    return
        year != this.year ? false : 
        area == "year" ? true :
        month != this.div ? false :
        area == "month" ? true :
        day != this.day ? false :
        area == "day";
}

Which could then be written into a single line:

checkData(day, month, year, area)
{
    return year != this.year ? false : area == "year" ? true : month != this.div ? false : area == "month" ? true : day != this.day ? false : area == "day";
}

Some languages support such kind of syntax (e.g. C#):

checkData(day, month, year, area) => year != this.year ? false : area == "year" ? true : month != this.div ? false : area == "month" ? true : day != this.day ? false : area == "day";