Question

我是使用JSON和Javascript的新手，但我正在尝试对Reddit提供的JSON文件的各种值进行排序。在控制台中，我确实看到了来自console.log（posts）的数组和JSON值。但是，console.log（posts.length）语句返回0并且屏幕上没有显示任何内容，我怀疑这是由于我如何在数组中存储和/或检索JSON值。

＆＃13;

var minVotes = 5;
var subreddit = "askreddit";
var posts = [];
//Retrieve JSON from Reddit using JQuery
$.getJSON("https://www.reddit.com/r/" + subreddit + "/rising.json?limit=50", function foo(result) {
  $.each(result.data.children.slice(0, 50), function(i, post) {

    if (post.data.ups > minVotes) {
      //Push JSON data to array to be sorted later
      posts.push(post.data);
    }
  })
})

//Sort the array
posts.sort(function(a, b) {
  return parseInt(a.data.ups - a.data.num_comments) - parseInt(b.data.ups - b.data.num_comments);
});

console.log(posts);
console.log(posts.length); //returns 0 ???

//Display the content, which doesn't work
for (var i = 0; i < posts.length; i++) {
  $("#reddit-content").append('<br>' + "Title: " + posts[i].title);
  $("#reddit-content").append('<br>' + "Url: " + posts[i].url);
  $("#reddit-content").append('<br>' + "Upvotes: " + posts[i].ups);
  $("#reddit-content").append('<br>' + "Comments: " + posts[i].num_comments);
  $("#reddit-content").append('<hr>');

}

＆＃13;

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="reddit-content"></div>

＆＃13;

Answer 1

这是因为$.getJSON的异步性质。如果你在响应处理程序内对数组进行排序，它可以正常工作。

您在排序中还有另一个问题，即访问属性值。我不相信您需要parseInt，因为JSON.parse会将这些值作为数字返回。

＆＃13;

var minVotes = 5;
var subreddit = "askreddit";
//Retrieve JSON from Reddit using JQuery
$.getJSON("https://www.reddit.com/r/" + subreddit + "/rising.json?limit=50", function foo(result) {
  var posts = [];

  $.each(result.data.children.slice(0, 50), function(i, post) {
    if (post.data.ups > minVotes) {
      //Push JSON data to array to be sorted later
      posts.push(post.data);
    }
  });

  //Sort the array
  posts.sort(function(a, b) {
    return parseInt(a.ups - a.num_comments) - parseInt(b.ups - b.num_comments);
  });

  console.log(posts);
  console.log(posts.length);

  //Display the content, which doesn't work
  for (var i = 0; i < posts.length; i++) {
    $("#reddit-content").append('<br>' + "Title: " + posts[i].title);
    $("#reddit-content").append('<br>' + "Url: " + posts[i].url);
    $("#reddit-content").append('<br>' + "Upvotes: " + posts[i].ups);
    $("#reddit-content").append('<br>' + "Comments: " + posts[i].num_comments);
    $("#reddit-content").append('<hr>');
  }
});

＆＃13;

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="reddit-content"></div>

＆＃13;

从Javascript数组中检索JSON值

1 个答案: