Циклическая прокрутка слайдера

$(document).ready(function(){
  var currentPosition = 0;
  var slideWidth = 540;
  var slides = $('.slide');
  var numberOfSlides = slides.length;
 
  // Remove scrollbar in JS
  $('#slidesContainer').css('overflow', 'hidden');
 
  // Wrap all .slides with #slideInner div
  slides
    .wrapAll('<div id="slideInner"></div>')
    // Float left to display horizontally, readjust .slides width
    .css({
      'float' : 'left',
      'width' : slideWidth
    });
 
  // Set #slideInner width equal to total width of all slides
  $('#slideInner').css('width', slideWidth * numberOfSlides);
 
  // Insert controls in the DOM
  $('#slideshow')
    .prepend('<span class="control" id="leftControl">Clicking moves left</span>')
    .append('<span class="control" id="rightControl">Clicking moves right</span>');
 
  // Hide left arrow control on first load
  manageControls(currentPosition);
 
  // Create event listeners for .controls clicks
  $('.control')
    .bind('click', function(){
    // Determine new position
    currentPosition = ($(this).attr('id')=='rightControl') ? currentPosition+1 : currentPosition-1;
    
    // Hide / show controls
    manageControls(currentPosition);
    // Move slideInner using margin-left
    $('#slideInner').animate({
      'marginLeft' : slideWidth*(-currentPosition)
    });
  });
 
  // manageControls: Hides and Shows controls depending on currentPosition
  function manageControls(position){
    // Hide left arrow if position is first slide
    if(position==0){ $('#leftControl').show() } else{ $('#leftControl').show() }
    // Hide right arrow if position is last slide
    if(position==numberOfSlides-1){ $('#rightControl').show() } else{ $('#rightControl').show() }
  } 
});

    if(position==0){ $('#leftControl').show() } else{ $('#leftControl').show() }
    // Hide right arrow if position is last slide
    if(position==numberOfSlides-1){ $('#rightControl').show() } else{ $('#rightControl').show()

manageControls(currentPosition);
    // Move slideInner using margin-left
    if (currentPosition == 3) {currentPosition = 0);
    $('#slideInner').animate({
      'marginLeft' : slideWidth*(-currentPosition)
    });