console.log(json2[key2].id)未定义

Question

我有这个node.js代码：

var json2 = JSON.parse(body2);
console.log(json2)

var arrFound2 = Object.keys(json2).filter(function(key2) {
    console.log(json2[key2].id)
    return json2[key2].id;
}).reduce(function(obj2, key2){
    obj2 = json2[key2].attempts[0].duration;
       console.log(obj2)
       return obj2;
}, {});
//console.log(arrFound);
callback(null, arrFound2);
});

当我运行它时，console.log(json2)返回json，但console.log(json2[key2].id)返回undefined。我在这里做错了什么？

这是我的JSON：

{ id: 'local-1517179209543',
  name: 'TeraGen (5MB) 30146960-047c-11e8-afb5-17a9edeb2d55',
  attempts: 
       [ { startTime: '2018-01-28T22:40:07.941GMT',
       endTime: '2018-01-28T22:40:17.739GMT',
       lastUpdated: '2018-01-28T22:40:17.000GMT',
       duration: 9798,
       sparkUser: 'paulcarron',
       completed: true,
       endTimeEpoch: 1517179217739,
       startTimeEpoch: 1517179207941,
       lastUpdatedEpoch: 1517179217000 } ] }

Answer 1

下面是你需要做的：

您只需要return json2[key2];，而不是传递return json2[key2].id;

运行代码片段，您就会明白了

​

var json2 = { 
  id: 'local-1517179209543',
  name: 'TeraGen (5MB) 30146960-047c-11e8-afb5-17a9edeb2d55',
  attempts: 
       [ { startTime: '2018-01-28T22:40:07.941GMT',
       endTime: '2018-01-28T22:40:17.739GMT',
       lastUpdated: '2018-01-28T22:40:17.000GMT',
       duration: 9798,
       sparkUser: 'paulcarron',
       completed: true,
       endTimeEpoch: 1517179217739,
       startTimeEpoch: 1517179207941,
       lastUpdatedEpoch: 1517179217000 } ] };
console.log(json2);

var arrFound2 = Object.keys(json2).filter(function(key2) {
    console.log(key2 , ' -----> ', json2[key2]);
    return json2[key2];
}).reduce(function(obj2, key2){
    obj2 = json2[key2].attempts[0].duration;
       console.log(obj2)
       return obj2;
}, {});
//console.log(arrFound);
callback(null, arrFound2);

​

Answer 2

console.log(json2[key2].id)错误，因为筛选器函数将数组传递给回调函数。您正在链接Object.keys( json2 )上的filter函数，这意味着filter函数将获得json2对象的键。要获得JSON的值，只需使用json2[key2]

https://docs.microsoft.com/en-us/scripting/javascript/reference/filter-method-array-javascript