Trigger Alert When Slider Moves Left A Certain Amount

So, I am going to actually kill two birds with one stone. First off, I am trying to trigger an alert once the slider moves left to a specific degree. For example, once it goes to,

Solution 1:

This accomplishes both of the things that you wanted using the optional callback parameter in the animate function. It checks first to see if the variable C (the 0-based index of the current slide) is equal to 2 (3 in 1-based indexing), and shows an alert if it is. Then it checks to see if C is equal to 10 (which would mean that the slide currently being shown is the 9th one; The 9th image is just a duplicate of the 1st one) If it is on the 9th one, then jump back to the first one and trigger $("#right").click();.

$('#left, #right').click(function() {
    C = (this.id == 'right' ? ++C : --C) < 0 ? N - 1 : C % N;
    $('#slider').stop().animate({
        left: -C * W
    }, 300, function() {
        if (C == 2){alert("3rd");}
        if (C == 10) {
            $('#slider').css("left", "0");
            $('#right').click();
        }
    });
});

JSFiddle (Because CodePen's layout is weird to me)