Question

我正在尝试从天气应用返回的JSON访问JavaScript中的嵌套数组。但是，如果控制台未返回cannot return property of 'x' of undefined，我似乎无法访问任何数据。我可以肯定地说问题出在我与result的互动方式上，但是我不确定。有谁知道我如何从嵌套数组中正确访问数据？

这是我目前无法使用的代码：

const weather = require('weather-js');

var val;
var temp;
var final;

weather.find({search: 'Oceanside, CA', degreeType: 'F'}, function(err, result){         
  if (err) console.log(err);

  obj = JSON.stringify(result, null, 2);
  temp = result[2].current.temperature;
  console.log(temp);
  final = result[1].location.name;
  console.log(final)
});

这是我要与之交互的JSON：

[
  {
    "location": {
      "name": "Oceanside, CA",
      "lat": "33.197",
      "long": "-117.381",
      "timezone": "-8",
      "alert": "",
      "degreetype": "F",
      "imagerelativeurl": "http://blob.weather.microsoft.com/static/weather4/en-us/"
    },
    "current": {
      "temperature": "55",
      "skycode": "31",
      "skytext": "Mostly Clear",
      "date": "2018-12-18",
      "observationtime": "22:15:00",
      "observationpoint": "Oceanside, CA",
      "feelslike": "55",
      "humidity": "90",
      "winddisplay": "3 mph Southwest",
      "day": "Tuesday",
      "shortday": "Tue",
      "windspeed": "3 mph",
      "imageUrl": "http://blob.weather.microsoft.com/static/weather4/en-us/law/31.gif"
    },
    "forecast": [
      {
        "low": "46",
        "high": "64",
        "skycodeday": "29",
        "skytextday": "Partly Cloudy",
        "date": "2018-12-17",
        "day": "Monday",
        "shortday": "Mon",
        "precip": ""
      },
      {
        "low": "45",
        "high": "65",
        "skycodeday": "34",
        "skytextday": "Mostly Sunny",
        "date": "2018-12-18",
        "day": "Tuesday",
        "shortday": "Tue",
        "precip": "0"
      },
      {
        "low": "44",
        "high": "67",
        "skycodeday": "34",
        "skytextday": "Mostly Sunny",
        "date": "2018-12-19",
        "day": "Wednesday",
        "shortday": "Wed",
        "precip": "0"
      },
      {
        "low": "47",
        "high": "69",
        "skycodeday": "30",
        "skytextday": "Partly Sunny",
        "date": "2018-12-20",
        "day": "Thursday",
        "shortday": "Thu",
        "precip": "0"
      },
      {
        "low": "47",
        "high": "65",
        "skycodeday": "34",
        "skytextday": "Mostly Sunny",
        "date": "2018-12-21",
        "day": "Friday",
        "shortday": "Fri",
        "precip": "0"
      }
    ]
  }
]

这个问题不是访问/进程（嵌套）对象，数组或JSON的重复，因为据我所见，该页面上的答案处理的是多个元素的数组，而这个问题没有。

Answer 1

//try this its working
var j = [{
  "location": {
    "name": "Oceanside, CA",
    "lat": "33.197",
    "long": "-117.381",
    "timezone": "-8",
    "alert": "",
    "degreetype": "F",
    "imagerelativeurl": "http://blob.weather.microsoft.com/static/weather4/en-us/"
  },
  "current": {
    "temperature": "55",
    "skycode": "31",
    "skytext": "Mostly Clear",
    "date": "2018-12-18",
    "observationtime": "22:15:00",
    "observationpoint": "Oceanside, CA",
    "feelslike": "55",
    "humidity": "90",
    "winddisplay": "3 mph Southwest",
    "day": "Tuesday",
    "shortday": "Tue",
    "windspeed": "3 mph",
    "imageUrl": "http://blob.weather.microsoft.com/static/weather4/en-us/law/31.gif"
  },
  "forecast": [{
      "low": "46",
      "high": "64",
      "skycodeday": "29",
      "skytextday": "Partly Cloudy",
      "date": "2018-12-17",
      "day": "Monday",
      "shortday": "Mon",
      "precip": ""
    },
    {
      "low": "45",
      "high": "65",
      "skycodeday": "34",
      "skytextday": "Mostly Sunny",
      "date": "2018-12-18",
      "day": "Tuesday",
      "shortday": "Tue",
      "precip": "0"
    },
    {
      "low": "44",
      "high": "67",
      "skycodeday": "34",
      "skytextday": "Mostly Sunny",
      "date": "2018-12-19",
      "day": "Wednesday",
      "shortday": "Wed",
      "precip": "0"
    },
    {
      "low": "47",
      "high": "69",
      "skycodeday": "30",
      "skytextday": "Partly Sunny",
      "date": "2018-12-20",
      "day": "Thursday",
      "shortday": "Thu",
      "precip": "0"
    },
    {
      "low": "47",
      "high": "65",
      "skycodeday": "34",
      "skytextday": "Mostly Sunny",
      "date": "2018-12-21",
      "day": "Friday",
      "shortday": "Fri",
      "precip": "0"
    }
  ]
}];
console.log(j[0].current.temperature);
console.log(j[0].location.name);

Answer 2

这很简单。假设JavaScript中的数组定义为var myArray=[]

您会注意到您的JSON具有一个外部[]，在其中您具有1个外部{}，这意味着它在数组中的索引为0处具有1个元素。

因此，不要做result[2].current.temperature;，而要做result[0].current.temperature;

使用result[2]会给您未定义的内容，因为它不存在！

如何访问嵌套数组？

2 个答案: