Moving a li up and down a list with jQuery

$(function () {                                                                 
    $.fn.exchangePositionWith = function(selector) {                            
        var other = $(selector);                                                
        this.after(other.clone());                                              
        other.after(this).remove();                                             
    };                                                                          
                                                                                
    $(document).on('click', '.fa-chevron-down', function () {                   
        var ul = $(this).parents('ul'),                                         
            li_index = $(this).parents('li').index();                                                                                    
        ul.children('li:eq(' + li_index + ')').exchangePositionWith(ul.children('li:eq(' + (li_index+2) + ')'))
    });                                                                         
                                                                                
    $(document).on('click', '.fa-chevron-up', function () {                     
        var ul = $(this).parents('ul'),                                         
            li_index = $(this).parents('li').index();                           
        if (li_index > 1) {                                                     
            ul.children('li:eq(' + li_index + ')').exchangePositionWith(ul.children('li:eq(' + (li_index-2) + ')'))
        }                                                                       
    });                                                                         
});