javascript - 对象数组的对象。获取具有相同属性的所有值的长度

Question

我有一个看起来像这样的对象:

    var obj = {
      "array1": [
        {
          "label": "something1",
          "ref": "option2a"
        },
        {
          "label": "something2",
          "ref": "option2b"
        },
        {
          "label": "something3",
          "ref": "option2a"
        },
        {
          "label": "something4",
          "ref": "option2a"
        },
        {
          "label": "something5",
          "ref": "option2a"
        }
      ],
      "array2": [
        {
          "label": "something6 is the longest label",
          "ref": "option3a"
        },
        {
          "label": "Other",
          "ref": "option3b"
        }
      ]
    }

我想得到最长标签的长度。在这种情况下，我想返回 17。因为最长的标签是“somethinglongest”，长度为 17。

Answer 1

• 使用 .concat() 和 Object.values() 获取包含所有对象的单个数组。
• 对包含字符串长度的数组使用 .map()。
• 最后使用.reduce() 得到最长字符串的长度。

let data = {
    "array1": [
        {"label": "something1", "ref": "option2a"},
        {"label": "something2", "ref": "option2b"},
        {"label": "something3", "ref": "option2a"},
        {"label": "something4", "ref": "option2a"},
        {"label": "something5", "ref": "option2a"}
    ],
    "array2": [
        {"label": "somethinglongest", "ref": "option3a"},
        {"label": "Other", "ref": "option3b"}
    ]
};

let reducer = arr => [].concat(...Object.values(arr))
                       .map(({ label }) => label.length)
                       .reduce((r, c) => r > c ? r : c);

console.log(reducer(data));