如何检查数组为空并在Ajax的内容中显示消息？

Question

代码中发生的事情是，我们基于单选按钮单击显示一个RSS feed。 每个单选按钮的RSS提要并不总是具有内容，我希望在空白屏幕上显示一条消息。 谢谢！

<script type="text/javascript">
  $(document).ready(function() {

    $('input[type=radio]').click(function() {

        var id = this.id;

        if(id == 'radio-bio') { var categoryURL = '/BayAreaTech/wp-rss2.php?cat=15';}
        else if (id == 'radio-com'){ var categoryURL = '/BayAreaTech/wp-rss2.php?cat=13';}
        else if (id == 'radio-eleP'){ var categoryURL = '/BayAreaTech/wp-rss2.php?cat=9';}
        else if (id == 'radio-eleD'){ var categoryURL = '/BayAreaTech/wp-rss2.php?cat=10';}
        else if (id == 'radio-nano'){ var categoryURL = '/BayAreaTech/wp-rss2.php?cat=16';}
        else if (id == 'radio-opt'){ var categoryURL = '/BayAreaTech/wp-rss2.php?cat=12';}
        else if (id == 'radio-semi'){ var categoryURL = '/BayAreaTech/wp-rss2.php?cat=11';}
        else if (id == 'radio-comSoft'){ var categoryURL = '/BayAreaTech/wp-rss2.php?cat=14';}
        else if (id == 'radio-techMan'){ var categoryURL = '/BayAreaTech/wp-rss2.php?cat=17';}
        else { var categoryURL = '/BayAreaTech/wp-rss2.php?cat=1';}

        $('#feedContainer').empty();
                    $.ajax({
                    type: 'GET',
                    url: categoryURL,
                    dataType: 'xml',
                    success: function (xml) {
                        var data = [];
            $(xml).find("item:lt(40)").each(function () {
                var dateText = $(this).find("Date").text().toString();
                var eventDate = moment(dateText,"YYYY-MM-DD");
                var title = $(this).find("title").text();

                var region = dateText.substr(8).toUpperCase();

                      if (region.length < 3) { region = "SF"; } 

                var description = $(this).find("description").text();
                var infoDisplay = description.substr(0, description.indexOf(",")+120) + "..."; //Parsed DATE from description

                  //var locationdisplay = description.substr(description.indexOf(",")+6,4); //Parsed the location from description
                var category = $(this).find("category").text();
                var linkUrl = $(this).find("link").text();
                var displayTitle = "<a href='" + linkUrl + "' target='_blank'>" + title + "</a>" 


                var item = {title: displayTitle, infoDecription: infoDisplay, Date: new Date(eventDate), Region: region,}
                var now = moment();
                if (item.Date >= now){ data.push(item); }



               // $('#feedContainer').append('<h3>'+displaytitle+'</h3><p>'+"Event Date: "+descriptdisplay+'</p><p>'+"Location: "+region+'</p');

            });
                 data.sort(function (a, b) {
                 a = new Date(a.Date);
                 b = new Date(b.Date);
                 return a<b ? -1 : a>b ? 1 : 0;
                 });

                 $.each(data, function (index, item) {
                 $('#feedContainer').append('<h3>' + item.title + '</h3><p>' + item.infoDecription + '</p>');
                 });
                    }
                });

      $("#fieldpanel").panel("close");
    });
 });
 </script>

Answer 1

您可以检查数组的长度

if (data.length > 0) {
    data.sort(function (a, b) {
        a = new Date(a.Date);
        b = new Date(b.Date);
        return a<b ? -1 : a>b ? 1 : 0;
    });

    $.each(data, function (index, item) {
         $('#feedContainer').append('<h3>' + item.title + '</h3><p>' + item.infoDecription + '</p>');
    });
}
else {
    $("#feedContainer").append('<h3>There is no content to display</h3>');
}