gistfile1.js

$(document).ready(function() {

    var directions = {
        'east': {
            value: 1,
            class: 'fromWest'
        },
        'southeast': {
            value: 4,
            class: 'fromNorthwest'
        },
        'south': {
            value: 3,
            class: 'fromNorth'
        },
        'southwest': {
            value: 2,
            class: 'fromNorthEast'
        },
        'west': {
            value: -1,
            class: 'fromEast' 
        }
    }

    $('.block').each(function() {

        $(this).removeAttr('direction');

        var dirs  = $(this).attr('direction').split(' ');
        var index = $('.block').index(this);

        for(var i = 0; i < dirs.length; i++) {

            var dir = dirs[i];
            var direction = directions[dir];

            if(!dir) {
                $(this).append('<span class="arrow ' + dir + '"></span>');
            }

            var id = index + direction.value;

            $('.block:eq(' + id + ')').append('<span class="arrow ' + direction.class + '"></span>');;

        }

    });

});