menu = new Slider('menu','menu-wrapper');

function Slider(menu,wrapper) {
    this.active = false;
    this.getWrapper = function getWrapper() { return wrapper; }
    this.getMenu = function getMenu() { return menu; }
}   // end of Slider(identifier)


Slider.prototype.startSlideLeft = function startSlideLeft() {
    var menu = document.getElementById(this.getMenu());
    var slides = menu.getElementsByTagName("li");
    
    left = menu.style.left;
    left = Number(left.substring(0,left.indexOf('px')));
    
    if (left < 0) {
    var moveBy = 8;
    Slider.intId = setInterval(function() {
    left = menu.style.left;
    left = Number(left.substring(0,left.indexOf('px')));
		if (left < 0){
			menu.style.left = (left + moveBy) + 'px'
		}else {
			clearInterval(Slider.intId);
		}
	}, 20);
	
	};
}   // Slider.prototype: end of slideLeft()


Slider.prototype.stopSlideLeft = function stopSlideLeft() {
			clearInterval(Slider.intId);
}   // Slider.prototype: end of slideLeft()








Slider.prototype.startSlideRight = function startSlideRight() {
    var menu = document.getElementById(this.getMenu());
    var slides = menu.getElementsByTagName("li");
    
    var wrapper = document.getElementById(this.getWrapper());
    
    var menuWidth = 0;
    for (i=1;i <= slides.length;i++){
        menuWidth += slides[i-1].offsetWidth;
    
    }
    
    left = menu.style.left;
    left = Number(left.substring(0,left.indexOf('px')));
    
    dif = wrapper.offsetWidth - menuWidth;
    
    var step = this.step;
    if (-(dif-left) < step) step = -(dif-left); // last step can be shorter
    if (dif < left) {    
    var moveBy = 8;
    Slider.intId = setInterval(function() {
    left = menu.style.left;
    left = Number(left.substring(0,left.indexOf('px')));
    
    dif = wrapper.offsetWidth - menuWidth;
		if (dif < left){
			menu.style.left = (left - moveBy) + 'px'
		}else {
			clearInterval(Slider.intId);
		}
	}, 20);
    
    
    };
}   // Slider.prototype: end of slideRight()

Slider.prototype.stopSlideRight = function stopSlideRight() {
			clearInterval(Slider.intId);
}   // Slider.prototype: end of slideLeft()