Javascript 为什么给出错误：无法读取属性'；类别'；未定义的？

我有一个旧的过时的脚本，我重新开始工作，并一直在努力改进。它在Blogspot上用于抓取帖子并随机显示，或者按标签显示最近的帖子

以下是脚本：

<script>
  /***
  THIS IS A SCRIPT TO USE WITH BLOGGER/BLOGSPOT HTML GADGET TO SHOW RECENT/RANDOM POSTS.
  ***/
  /*** LET'S ADD THE VARIABLE SETINGS. TO TOGGLE USE TRUE/FALSE ***/
  var domainURL = window.location.hostname;
  var className = 'default';
  var postCount = 3;
  var showPostLabel = 'test';
  var showPostContentAmount = 160;
  var showPostTitle = 'true';
  var showPostTitleAmount = 80;
  var showInPostImageSize = 320;
  var showPostComments = 'true';
  var showPostDate = 'true';
  var showPostAuthor = 'true';
  var showPostImage = 'true';
  var showPostCategory = 'true';
  var showPostTags = 'true';
  var showPostContent = 'true';
  var showCategoryArchive = 'true';
  var showRandomPosts = 'true';

  /*** LET'S ADD THE RANDOM ARRAY ***/
  var RandomArray = [];
  var TotalPosts  = 0;
  var RandomArray = new Array(postCount);

  function TotalCount(json) {
  TotalPosts   = json.feed.openSearch$totalResults.$t
  }
  document.write('<script type=\"text/javascript\" src=\"https://'+domainURL+'/feeds/posts/default?alt=json-in-script&callback=TotalCount\"><\/script>');

  function GenerateNum() {
  for (var i = 0; i < postCount ; i++) {
  for (var j = 0; j < RandomArray.length; j++){
  var RandomNum = Math.floor(Math.random() * (TotalPosts ) + 1);
  RandomArray[i] = RandomNum; }
                                     }
  }
  </script>
  <script>

  /*** LET'S START THE POST LIST ***/
  document.write('<ul class="json-posts '+className+'">');

  /*** LET'S START THE FUNCTION ***/
  function jsonposts(json)
  {

    for (var i = 0; i < postCount; i++)
    {

      /*** LET'S DECLARE VARIABLES ***/
      var postVariables = postImage = postUrl = postTitle = postImage = postContent = postArticle = postAuthor = postTags = postCategory = postDate = postUpdated = postComment = postImageURL = postCategoryArchive = postImageURLSize = postAuthorImage = postDateFormat = Y = D = M = m = YY = DD = MM = mm = TT =  "";

      /*** LET'S GET THE POST LABELS ***/
      if (json.feed.entry[i].category != null && json.feed.entry[i].category.length > 0)
      {
        postCategory += '<a class="json-post-article-category" href="'+domainURL+'/search/label/'+json.feed.entry[i].category[0].term+'">'+json.feed.entry[i].category[0].term+'</a>';
      }

      /*** LET'S GET THE POST LABELS ***/
      if (json.feed.entry[i].category != null)
      {
        for (var k = 0; k < json.feed.entry[i].category.length; k++)
        {
          postTags += '<a class="json-post-article-tag-item" href="'+domainURL+'/search/label/'+json.feed.entry[i].category[k].term+'">'+json.feed.entry[i].category[k].term+'</a>';
          if(k < json.feed.entry[i].category.length-1)
          {
            postTags += '<span class="json-post-article-tag-item-seperator">, </span>';
          }
        }
      }

      /*** LET'S GET THE POST URL ***/
      for (var j = 0; j < json.feed.entry[i].link.length; j++)
      {
        if (json.feed.entry[i].link[j].rel == 'alternate')
        {
          break;
        }
      }
      postUrl= '"' + json.feed.entry[i].link[j].href + '"';

      /*** LET'S GET THE POST INFO ***/
      postCategoryArchive = json.feed.openSearch$totalResults.$t;

      /*** LET'S GET THE POST TITLE ***/
      if (json.feed.entry[i].title!= null)
      {
        postTitle= json.feed.entry[i].title.$t.substr(0, showPostTitleAmount);
      }

      /*** LET'S GET THE POST COMMENT COUNT ***/
      if (json.feed.entry[i].thr$total)
      {
        postComment = '<a href="'+json.feed.entry[i].link[j].href+'#comment-form">'+json.feed.entry[i].thr$total.$t+'</a>';
      }

      /*** LET'S GET THE POST AUTHOR INFO ***/
      postAuthor = json.feed.entry[i].author[0].name.$t.split(' ');
      postAuthor = postAuthor.slice(0, 1).join(' ');
      postAuthorImage = json.feed.entry[i].author[0].gd$image.src;

      /*** LET'S GET THE POST CONTENT ***/
      postArticle = json.feed.entry[i].content.$t;
      postContent = postArticle.replace(/(<([^>]+)>)/ig,'').substring(0, showPostContentAmount);

      /*** LET'S FORMAT THE POST DATE MONTH ***/
      postDateFormat= ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'];

      /*** LET'S GET THE POST DATE ***/
      postDate= json.feed.entry[i].published.$t.substring(0,10);

      /*** LET'S DO THE POST DATE FORMAT ***/
      Y = postDate.substring(0, 4);
      m = postDate.substring(5, 7);
      D = postDate.substring(8, 10);
      M = postDateFormat[parseInt(m - 1)];

      /*** LET'S GET THE UPDATED POST DATE ***/
      postUpdated= json.feed.entry[i].updated.$t.substring(0, 16);

      /*** LET'S DO THE UPDATED POST DATE FORMAT ***/
      YY = postUpdated.substring(0, 4);
      mm = postUpdated.substring(5, 7);
      DD = postUpdated.substring(8, 10);
      TT = postUpdated.substring(11, 16);
      MM = postDateFormat[parseInt(mm - 1)];

      /*** LET'S GET THE POST IMAGE ***/
      if (json.feed.entry[i].media$thumbnail)
      {
        postImageURL = json.feed.entry[i].media$thumbnail.url;
        postImageURLSize = postImageURL.replace("/s72-c/","/s"+showInPostImageSize+"/");
        postImageURLSize = postImageURL.replace("default.jpg","mqdefault.jpg");
      }

      /*** LET'S OPEN THE POST ARTICLE ***/
      document.write('<li class="json-post-article"><article itemprop="blogPost" itemscope="itemscope" itemtype="https://schema.org/BlogPosting">');

      /*** LET'S SHOW THE POST CATEGORY ***/
      if (showPostCategory == 'true')
      {
        document.write('<div class="json-post-article-category"><span class="json-post-article-category-label">Category: </span>'+postCategory+'</div>');
      }

      /*** LET'S SHOW THE POST IMAGE ***/
      if (showPostImage == 'true')
      {
        document.write('<a class="json-post-article-featured-image-link" href="'+postUrl+'" itemprop="url"><figure class="json-post-article-featured-image" style="background-image: url('+postImage+')"></figure></a>');
      }

      /*** LET'S OPEN THE POST INFO BOX ***/
      document.write('<div>');

      /*** LET'S SHOW THE POST TITLE ***/
      if (showPostTitle == 'true')
      {
        document.write('<h4 class="json-post-article-title" itemprop="name"><a class="json-post-article-title-link" href="'+postUrl+'" itemprop="url">'+postTitle+'</a></h4>');
      }

      /*** LET'S SHOW THE POST AUTHOR ***/
      if (showPostAuthor == 'true')
      {
        document.write('<div class="json-post-article-author"><span class="json-post-article-author-label" itemprop="author">Author: </span><figure class="json-post-article-author-avatar" style="background: url(https:'+postAuthorImage+')"></figure><span class="json-post-article-author-name">'+postAuthor+'</span></div>');
      }

      /*** LET'S SHOW THE POST DATE ***/
      if (showPostDate == 'true')
      {
        document.write('<div class="json-post-article-date" itemprop="datePublished"><span class="json-post-article-date-label">Date: </span><span class="json-post-article-date-month">'+M+'</span> <span class="json-post-article-date-day">'+D+'</span> <span class="json-post-article-date-year">'+Y+'</span></div>');
      }

      /*** LET'S SHOW THE POST CONTENT ***/
      if (showPostContent == 'true')
      {
        document.write('<p class="json-post-article-content">'+postContent+'...</p>');
      }

      /*** LET'S SHOW THE POST TAGS ***/
      if (showPostTags == 'true')
      {
        document.write('<div class="json-post-article-tags"><span class="json-post-article-tags-label">Tags: </span>'+postTags+'</div>');
      }

      /*** LET'S SHOW THE POST COMMENT COUNT ***/
      if (showPostComments == 'true')
      {
        document.write('<div class="json-post-article-comment-count"><span class="json-post-article-comment-count-label">Comments: </span><span class="json-post-article-comment-count-number">'+postComment+'</span></div>');
      }

      /*** LET'S CLOSE THE POST INFO BOX ***/
      document.write('</div>');

      /*** LET'S CLOSE THE POST ARTICLE ***/
      document.write('</article></li>');

    }

    /*** LET'S SHOW THE POST CATEGORY ARCHIVE LINK ***/
    if (showCategoryArchive == 'true')
    {
      document.write('<a class="json-post-article-category-more" href="'+domainURL+'/search/label/'+showPostLabel+'">More</a>');
    }

  }

  /*** LET'S SHOW THE POST AS RANDOM OR ELSE AS RECENT ***/
  if (showRandomPosts == 'true')
  {

    for (var i = 0; i < postCount ; i++)
    {
      GenerateNum();
      document.write('<script type=\"text/javascript\" src=\"https://'+domainURL+'/feeds/posts/default?alt=json-in-script&start-index=' + RandomArray[i] + '&max-results=1&callback=jsonposts\"><\/script>')
    }

  }
  else
  {
    document.write('<script type=\"text/javascript\" src=\"https://'+domainURL+'/feeds/posts/default/-/'+showPostLabel+'?alt=json-in-script&callback=jsonposts\"><\/script>')
  }

  document.write('</ul>');
</script>

---

很难理解JSON的结构，因为我们不知道传递给

jsonposts

函数的是什么。该错误很好地描述了问题所在，但您需要使用或获取更多信息

我看到您在代码中9次访问

类别

属性，每次都是在

json.feed.entry[I]

上访问它们，这让我相信

entry

数组中的

entry

元素之一是

未定义的

。一种可能是

postCount

高于

json.feed.entry

数组的

长度

看看我的复制品，看看什么时候会发生


var postCount=5；
var json={
提要：{
条目：[{category:{term:'test'}，{category:{term:'test2'}}]
}
}
对于（变量i=0；i}
postCount
高于
json.feed.entry
数组不是问题。我仍在努力理解您的其他建议。如果您将
showRandomPosts
设置为非true，则不会出现错误。问题必须是随机数组代码。