JavaScript Help combining two functions

[jack]

Hi,
I have these two functions which have mostly similar code.. so I want to combine them into one function.. any help appreciated.

previousMonthImg.onclick = function() {
    if (!(monthSelect.value === "Jan" && yearSelect.value === "2010")) {
        monthSelect.selectedIndex--;
        if (monthSelect.selectedIndex === -1) {
            monthSelect.value = "Dec";
            yearSelect.selectedIndex--;
        }
    }
    triggerEvent(monthSelect, "change");
    triggerEvent(yearSelect, "change");
};

nextMonthImg.onclick = function() {
    if (!(monthSelect.value === "Dec" && yearSelect.value === "2030")) {
        monthSelect.selectedIndex++;
        if (monthSelect.selectedIndex === -1) {
            monthSelect.value = "Jan";
            yearSelect.selectedIndex++;
        }
    }
    triggerEvent(monthSelect, "change");
    triggerEvent(yearSelect, "change");
}

 

[Mutiny]

Honestly, looking at these two functions they are pretty similar, but have one key difference: The first one subtracts values and the second one adds to them. You could combine them into one big function, but then you have to do a bunch of if checks to see if you are incrementing or decrementing the value. You also have to then keep track of whether the user clicked the previous or next month image.

I would recommend maybe making a third function called activateCalendarTriggers that has the triggerEvent() code in it and call that function from both of these functions. That may be the cleaner solution as you'll be extracting out the code that is the same while keeping the code that is different in separate functions.