javascript - 从 json stringify 中提取文本

Question

我是 JSON Javascript 新手。我有一个对象，我只想提取文本值。

这是我的代码，但是当我运行它时，结果是未定义:

    var obj = [{
                "start_location":
                    {
                     "lat":47.951042801290065,
                     "lng":-116.70764186944393
                    },
                "end_location": 
                    {
                     "lat":47.94871454878046,
                     "lng":-116.70839074239734
                    },
                "length":
                    {
                     "text":"265.13 m",
                     "value":265.126074613001
                    }
               },
               {
                "start_location": 
                    {
                     "lat":47.94871454878046,
                     "lng":-116.70839074239734
                    },
                "end_location": 
                    {
                     "lat":47.949763712586105,
                     "lng":-116.70401337728504
                    },
                "length":
                    {
                     "text":"346.65 m",
                     "value":346.6461031139708
                    }
               },
               {
                "start_location": 
                    {
                     "lat":47.949763712586105,
                     "lng":-116.70401337728504
                    },
                "end_location": 
                    {
                     "lat":47.951042801290065,
                     "lng":-116.70764186944393
                    },
                "length":
                    {
                     "text":"305.72 m",
                     "value":305.7189215338448
                    }
               }
           ];

    var myJSON = JSON.stringify(obj);

    document.getElementById("demo").innerHTML = myJSON[['length'],['text']];

Answer 1

你为什么要对其进行字符串化。从 JS 对象中获取比 JSON 格式的字符串更容易。

var obj = [
  {
    "start_location": { "lat": 47.951042801290065, "lng": -116.70764186944393 },
    "end_location": { "lat": 47.94871454878046, "lng": -116.70839074239734 },
    "length": { "text": "265.13m", "value": 265.126074613001 }
  },
  {
    "start_location": { "lat": 47.94871454878046, "lng": -116.70839074239734 },
    "end_location": { "lat": 47.949763712586105, "lng": -116.70401337728504 },
    "length": { "text": "346.65m", "value": 346.6461031139708 }
  },
  {
    "start_location": { "lat": 47.949763712586105, "lng": -116.70401337728504 },
    "end_location": { "lat": 47.951042801290065, "lng": -116.70764186944393 },
    "length": { "text": "305.72m", "value": 305.7189215338448 }
  }
];

let lengths = obj.map(item => item.length.text);

console.log(lengths);