如何使用JavaScript访问JSON数据中嵌套数组中的特定元素？

Question

我有JSON数据，结构如下。内涵是查找特定的数据点，例如年利润，即5000。

我希望通过按名称查找列来完成此操作，例如“profit”，标识列索引（示例中为3），然后使用列索引选择“data”数组的第二个节点（“年”）中的第n个（第3个）元素。

如何在Javascript中使用findIndex()函数执行此操作（请参阅下面代码的关键部分）？

JSON数据：

{
  "datatable": {
    "data": [
      [
        "AAPL",
        "quarterly",
        1000,
        2000
      ],
      [
        "AAPL",
        "annual",
        5000,
        10000
      ]
    ],
    "columns": [{
        "name": "ticker"
        "type": "String"
      },
      {
        "name": "timedim"
        "type": "String"
      },
      {
        "name": "profit",
        "type": "Integer"
      },
      {
        "name": "revenue",
        "type": "Integer"
      }
    ]
  }
}

JavaScript代码：

  // daten contains the "data" array of the JSON dataset
  // spalten contains the "columns" array of the JSON dataset
  
  var i = spalten.findIndex(obj => obj.name == "profit");
  output += '<p>Annual profit AAPL: ' + daten[i] + '</p>';
  elroot.innerHTML += output;

Answer 1

你有2-dimensional数组，所以，你需要两个索引：

const json = {
  "datatable": {
    "data": [
      [
        "AAPL",
        "quarterly",
        1000,
        2000
      ],
      [
        "AAPL",
        "annual",
        5000,
        10000
      ]
    ],
    "columns": [{
        "name": "ticker",
        "type": "String"
      },
      {
        "name": "timedim",
        "type": "String"
      },
      {
        "name": "profit",
        "type": "Integer"
      },
      {
        "name": "revenue",
        "type": "Integer"
      }
    ]
  }
}
var profitIndex = json.datatable.columns.findIndex(item => item.name == 'profit');
var annualIndex = json.datatable.data.findIndex(array => array.indexOf('annual') > -1);
var annualProfit = json.datatable.data[annualIndex][profitIndex];

如果你需要一个函数，它可能如下所示：

var getValueFromJson = function (json, columnName, dataMarker) {
    var columnIndex = json.datatable.columns.findIndex(item => item.name == columnName);
    var dataMarkerIndex = json.datatable.data.findIndex(array => array.indexOf(dataMarker) > -1);
    if (columnIndex < 0 || dataMarkerIndex < 0) {
        return null;
    }
    return json.datatable.data[dataMarkerIndex][columnIndex];
}

console.log(getValueFromJson(json, 'profit', 'quarterly'));
console.log(getValueFromJson(json, 'profit', 'annual'));
console.log(getValueFromJson(json, 'revenue', 'quarterly'));
console.log(getValueFromJson(json, 'revenue', 'annual'));

上面的代码打印：

> 1000
> 5000
> 2000
> 10000

Answer 2

根据您给出的JSON结构，以下内容将起作用。如果您想根据参数获得特定利润，编写函数会很好。

  var output = ""
  function getProfit(type="annual", column=2) {
    var arrForType = yourData.datatable.data.find(arr => arr.indexOf(type) !== -1);
    return arrForType[column];
  }

  var i = yourData.datatable.columns.findIndex(obj => obj.name == "profit");
  output += '<p>Annual profit AAPL: ' + getProfit("annual", i) + '</p>';
  document.body.innerHTML += output;

Answer 3

你不需要findIndex - 只需使用find和includes：

const data = {
  "datatable": {
    "data": [
      [
        "AAPL",
        "quarterly",
        1000,
        2000
      ],
      [
        "AAPL",
        "annual",
        5000,
        10000
      ]
    ],
    "columns": [{
        "name": "ticker",
        "type": "String"
      },
      {
        "name": "timedim",
        "type": "String"
      },
      {
        "name": "profit",
        "type": "Integer"
      },
      {
        "name": "revenue",
        "type": "Integer"
      }
    ]
  }
};

function findValue(type) {
  return data.datatable.data.find(e => e.includes(type))[2];
}

console.log(findValue("annual"));
console.log(findValue("quarterly"));

Answer 4

这是基本的想法，那么如果你需要明显扩展，你需要以更好的方式做到这一点。

let output = '';

// Searches the desired index (refactor as needed)
const index = spalten.findIndex(obj => obj.name == "profit")

// Extract all the profits (if you dont need all just select the desired one)
daten.map(item => output += `<p>${item[1]} profit ${item[0]}: ${item[index]}</p>`)