JavaScript json 返回未定义

Question

所以我试图通过 for in 循环从 json 对象中获取一些数据，但它一直返回未定义。这是我的代码:

router.get('/', function(req, res, next) {
  request('https://api.instagram.com/v1/media/popular?client_id=############', function (error, response, body) {
    json = JSON.parse(body);
    var popular_tags = [];

    for (var key in json['data']){
      tag = JSON.stringify(key['tags'])
        popular_tags.push(tag)  
    }
    console.log(popular_tags)

    res.render('index', {title: body });
  });
});

这是我收到的输出:

[ undefined,
  undefined,
  undefined,
  undefined,
  undefined,
  undefined,
  undefined,
  undefined,
  undefined,
  undefined,
  undefined,
  undefined,
  undefined,
  undefined,
  undefined,
  undefined,
  undefined,
  undefined,
  undefined,
  undefined ]

但是，当我尝试

var popular_tags = [];
popular_tags.push(json['data'][0]['tags'])
console.log(popular_tags)

它会打印出我想要的内容。有什么建议吗？

Answer 1

将行更改为

tag = JSON.stringify(json['data'][key]['tags'])