Untitled

How to select the last element on viewport
$(window).scroll(function () {

$('.post-content p').removeClass("temp last")
$('.post-content p').filter(":onScreen").addClass("temp")

$(".temp").eq(-1).addClass("last")

    });

// Store the offsets in an array
var offsets = [];
// Cache the elements to select
var elements = $('.elem');
// Cache the window jQuery Object
var jWindow = $(window);
// Cache the calculation of the window height
var jWindowHeight = jWindow.height();
// set up the variable for the current selected offset
var currentOffset;
// set up the variable for the current scrollOffset
var scrollOffset;
// set up the variable for scrolled, set it to true to be able to assign at
// the beginning
var scrolled = true;

// function to assign the different elements offsets,
// they don't change on scroll
var assignOffsets = function() {
    elements.each(function() {
        offsets.push({
            offsetTop: $(this).offset().top,
            height: $(this).height(),
            element: $(this)
        });
    });
};

// execute the function once. Exectue it again if you added
// or removed elements
assignOffsets();

// function to assign a class to the last element
var assignLast = function() {
    // only execute it if the user scrolled
    if (scrolled) {
        // assigning false to scrolled to prevent execution until the user
        // scrolled again
        scrolled = false;

        // assign the scrolloffset
        scrollOffset = jWindowHeight + jWindow.scrollTop();

        // only execute the function if no current offset is set,
        // or the user scrolled down or up enough for another element to be
        // the last
        if (!currentOffset || currentOffset.offsetTop < scrollOffset || currentOffset.offsetTop + currentOffset.height > scrollOffset) {

            // Iterate starting from the bottom
            // change this to positive iteration if the elements count below
            // the fold is higher than above the fold
            for (var i = offsets.length - 1; i >= 0; i--) {

                // if the element is above the fold, reassign the current
                // element
                if (offsets[i].offsetTop + offsets[i].height < (scrollOffset)) {
                    currentOffset && (currentOffset.element.removeClass('last'));
                    currentOffset = offsets[i];
                    currentOffset.element.addClass('last');
                    // no further iteration needed and we can break;
                    break;
                }
            }
            return true;
        } else {
            return false;
        }
    }
}

assignLast();

// reassign the window height on resize;
jWindow.on('resize', function() {
    jWindowHeight = jWindow.height();
});

// scroll handler only doing assignment of scrolled variable to true
jWindow.scroll(function() {
    scrolled = true;
});

// set the interval for the handler
setInterval(assignLast, 250);

// assigning the classes for the first time
assignLast();