$('.portfolio-slider .slide-button').on('click',function(){
    var buttonPrev = $(this).hasClass('slide-prev'), buttonNext = $(this).hasClass('slide-next');
    var slideBlock = $('.portfolio-slider .-slide'), slideActive = $('.portfolio-slider .-slide.slide-active');
    var slideLen = slideBlock.length, slideActiveIndex = slideActive.index();

    slideBlock.removeClass('slide-active');

    if(buttonPrev) {
        slideBlock.eq(slideActiveIndex-1).addClass('slide-active');
        console.info('slide: '+(slideActiveIndex-1)+'/'+slideLen);
    }
    if(buttonNext) {
        slideBlock.eq(slideActiveIndex+1).addClass('slide-active');
        console.info('slide: '+(slideActiveIndex+1)+'/'+slideLen);
    }
});