addAdjacent.js

/**
 * Can set a class to last element in a row of elements floating left.
 *
 * @param {String} list elements (ul li).
 * @param {String}
 * @returns {undefined}
 */
var setClassToLastElementInRow = function(selector, className) {
    var elements = $(selector);
    elements.each(function() {
        if($(this).prev().length > 0) {
            if($(this).position().top !== $(this).prev().position().top) {
                $(this).prev().addClass(className);
            }
        }
    });
};

calculateListItemsInRow.js

function calculateListItemsInRow(selector) {
    var element = $(selector);
    var lisInRow = 0;
    element.each(function() {
        if($(this).prev().length > 0) {
            if($(this).position().top != $(this).prev().position().top) return false;
            lisInRow++;
        }
        else {
            lisInRow++;   
        }
    });
    console.log('No: of lis in a row = ' + lisInRow);
}