localStorage Add to Cart

I'm creating a simple add to cart feature using jQuery and localStorage. Everything works fine, but I cannot add a selected class to the Add to Cart button. Please help me to add and remove (toggle) the selected class.

I need the logic to set the class on the buttons based on whether or not the product is held in the JSON I am holding in localStorage.

var favorites = JSON.parse(localStorage.getItem('favorites')) || [];
var list = $("#fav-list");
var parent = list.parent();

function addFavList() {
  list.detach().empty().each(function(i) {
    for (var x = 0; x < favorites.length; x++) {
      $(this).append('<li>' + favorites[x] + '</li>');
      if (x == favorites.length - 1) {
        $(this).appendTo(parent);
      }

    }
  });
}

addFavList();

$(document).delegate('.cart', 'click', function(e) {
  var id = $(this).parent().html(),
    index = favorites.indexOf(id);

  if (!id) 
    return;

  if (index == -1) {
    favorites.push(id);
  } else {
    favorites.splice(index, 1);
    $(this).parent().removeClass('fav');
  }

  localStorage.setItem('favorites', JSON.stringify(favorites));
  addFavList();
});


$(document).delegate('#delete', 'click', function() {
  localStorage.clear();
  location.reload();
});

Please check this Fiddle where I have tried my best

from localStorage Add to Cart