为什么CSS加载器一直出现在所有项目加载后?

Question

我一直在做一个在线报纸/博客应用程序CodeIgniter 3.1.8和Twitter Bootstrap 4.

我目前正在通过AJAX加载更多的帖子。

默认情况下，对帖子进行分页，每次显示12，在http://myblog.com/,http://myblog.com/?page=2，等等。

在Posts控制器(applicationcontrollersPosts.php)我有

private function _initPagination($path, $totalRows, $query_string_segment = 'page')
{
//load and configure pagination 
$this->load->library('pagination');
$config['base_url']             = base_url($path);
$config['query_string_segment'] = $query_string_segment;
$config['enable_query_strings'] = TRUE;
$config['reuse_query_string']   = TRUE;
$config['total_rows']           = $totalRows;
$config['per_page']             = 12;
if($this->Static_model->get_static_data()['has_pager']){
$config['display_pages'] = FALSE;
$config['first_link'] = FALSE;
$config['last_link'] = FALSE;
$config['prev_tag_open'] = '<li class="prev">';
$config['prev_tag_close'] = '</li>';
$config['next_tag_open'] = '<li class="next">';
$config['next_tag_close'] = '</li>';
}
if (!isset($_GET[$config['query_string_segment']]) || $_GET[$config['query_string_segment']] < 1) {
$_GET[$config['query_string_segment']] = 1;
}
$this->pagination->initialize($config);

$limit  = $config['per_page'];
$offset = ($this->input->get($config['query_string_segment']) - 1) * $limit;

return array(
'limit' => $limit,
'offset' => $offset
);
}
public function index()
{
//call initialization method
$config = $this->_initPagination("/", $this->Posts_model->get_num_rows());
$data                  = $this->Static_model->get_static_data();
$data['base_url']      = base_url("/");
$data['pages']         = $this->Pages_model->get_pages();
$data['categories']    = $this->Categories_model->get_categories();
$data['search_errors'] = validation_errors();

//use limit and offset returned by _initPaginator method
$data['posts'] = $this->Posts_model->get_posts($config['limit'], $config['offset']);
$this->twig->addGlobal('pagination', $this->pagination->create_links());

// featured posts
if ($data['is_featured']) {
$data['featured'] = $this->Posts_model->featured_posts();
$this->twig->addGlobal('featuredPosts', "themes/{$data['theme_directory']}/partials/hero.twig");
}

$this->twig->display("themes/{$data['theme_directory']}/layout", $data);
} 

为了通过jQuery Ajax加载帖子，我有:

(function($) {
var currentPage = 1;
$('.pagination').hide();
$(window).scroll(function() {
if ($(window).scrollTop() >= $(document).height() - $(window).height() - 10) {
loadMore();
}
});
function loadMore() {
$.ajax({
url: baseUrl + '?page=' + currentPage,
type: 'GET',
beforeSend: function() {
$('.loader').show();
}
})
.done(function(data) {
$('.loader').hide();
// Get post from page 2 onward
if (currentPage >= 2) {
var posts = $(data).find('#postsContainer').html();
}
// If there are no more posts, hide loader
//  Otherwise, load more posts
if (posts == 'undefined') {
$('.loader').hide();
} else {
$('#postsContainer').append(posts);
currentPage = currentPage + 1;
}
});
}
})(jQuery);

问题:

加载上一篇文章后，如果我向上(或上下)滚动，加载器会反复显示和隐藏。

---

我做错了什么?我如何修复这个bug?

Answer 1

我通过用null初始化变量posts并确保posts不是undefined在显示加载器之前解决了这个问题:

(function($) {
var currentPage = 2,
maxPage = $('#postsContainer').data('max-page'),
posts = null;
$('.pagination').hide();
$(window).scroll(function() {
var toBottom = $(window).scrollTop() >= $(document).height() - $(window).height() - 25;
if (toBottom && currentPage <= maxPage) {
loadMore();
}
});
function loadMore() {
$.ajax({
url: baseUrl + '?page=' + currentPage,
type: 'GET',
beforeSend: function() {
if (typeof posts != 'undefined') {
$('.loader').show();
}
}
})
.done(function(data) {
$('.loader').hide();
posts = $(data).find('#postsContainer').html();
if (typeof posts != 'undefined') {
$('#postsContainer').append(posts);
currentPage = currentPage + 1;
if (currentPage > maxPage) {
$('#postsContainer').append('<p class="text-center text-muted">No more posts to load</p>');
}
}
});
}
})(jQuery);

在控制器中:

public function index()
{
//call initialization method
$config = $this->_initPagination("/", $this->Posts_model->get_num_rows());
$data                  = $this->Static_model->get_static_data();
$data['base_url']      = base_url("/");
$data['pages']         = $this->Pages_model->get_pages();
$data['categories']    = $this->Categories_model->get_categories();
$data['search_errors'] = validation_errors();
$data['posts'] = $this->Posts_model->get_posts($config['limit'], $config['offset']);
$data['max_page'] = ceil($this->Posts_model->get_num_rows() / 12);
$this->twig->addGlobal('pagination', $this->pagination->create_links());
// Featured posts
if ($data['is_featured']) {
$data['featured'] = $this->Posts_model->featured_posts();
$this->twig->addGlobal('featuredPosts', "themes/{$data['theme_directory']}/partials/hero.twig");
}
$this->twig->display("themes/{$data['theme_directory']}/layout", $data);
}

在视图中:

<div id="postsContainer" data-max-page="{{max_page}}">