javascript - 仅当数据来自循环 GET 请求时，JSON stringify 才会失败

Question

所以当我尝试创建 JSON 字符串时遇到问题。只有当我用来构建将被字符串化的对象/数组的数据来自循环中的 GET 请求时，我才会遇到问题。

当我将实际的 javascript 对象发布到控制台时，它包含所有正确的信息。但无法生成有效的 JSON 字符串。我已经测试了这种方法(下面的示例)并且知道它有效。我得出的结论是这与 GET 请求有关。我尝试了几种解决方案；玩过变量作用域、异步流控制，但仍然没有运气。因此我就在这里。我错过了什么？

谢谢大家

这是有问题的代码:

 var start = 1518;
var end = 1522;
var eventList = {};
eventList['event'] = [];

for (var i = 0; i < (end - start); i++) {
  $.get('https://www.someaddress.com/events/index.php?view=' + (start + i), function(response) {

    var eventRep = $(response).find('h2').text();
    var categoryRep = $(response).find('span.center-name').text();
    var descriptionRep = $(response).find('div.description.col-md-9').find('p').text();

    var eventScrape = {
      "title": eventRep,
      "category": categoryRep,
      "description": descriptionRep
    };
    //alert(eventRep); 
    eventList['event'].push(eventScrape);
  });
}

var str = JSON.stringify(eventList, undefined, 4);
console.log(eventList);
console.log(str);

生成失败的 JSON:

    {
    "event": []
}

这是我想要的一个工作示例:

  var eventList = {};
  eventList['event'] = [];


  for (var i = 0; i < 5; i++) {
    var eventRep = "Event title " + i;
    var categoryRep = "Event category " + i;
    var descriptionRep = "Event description " + i;

    var eventScrape = {
      "title": eventRep,
      "category": categoryRep,
      "description": descriptionRep
    };

    eventList['event'].push(eventScrape);
    //alert(i);
  }

  var str = JSON.stringify(eventList, undefined, 4);
  console.log(eventList);
  console.log(str);

示例生成的 JSON:

{  
   "event":[  
      {  
         "title":"Event title 0",
         "category":"Event category 0",
         "description":"Event description 0"
      },
      {  
         "title":"Event title 1",
         "category":"Event category 1",
         "description":"Event description 1"
      },
      {  
         "title":"Event title 2",
         "category":"Event category 2",
         "description":"Event description 2"
      },
      {  
         "title":"Event title 3",
         "category":"Event category 3",
         "description":"Event description 3"
      },
      {  
         "title":"Event title 4",
         "category":"Event category 4",
         "description":"Event description 4"
      }
   ]
}

Answer 1

$.get 以异步方式执行，因此请将代码放入 get 函数

解决方案代码

var start = 1518;
var end = 1522;
var eventList = {};
eventList['event'] = [];

for (var i = 0; i < (end - start); i++) {
  $.get('https://www.someaddress.com/events/index.php?view=' + (start + i), function(response) {

    var eventRep = $(response).find('h2').text();
    var categoryRep = $(response).find('span.center-name').text();
    var descriptionRep = $(response).find('div.description.col-md-9').find('p').text();

    var eventScrape = {
      "title": eventRep,
      "category": categoryRep,
      "description": descriptionRep
    };
    //alert(eventRep); 
    eventList['event'].push(eventScrape);

    //as $.get is async data will be loaded in async manner so you cannot access it unless it is available
    var str = JSON.stringify(eventList, undefined, 4);
    console.log(eventList);
    console.log(str);
  });
}