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"
        }
      ]
    }

我想获得最长标签的长度。 在这种情况下，我想返回17.因为最长的标签是“somethinglongest”，其长度为17。

Answer 1

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

 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)); 

Answer 2

获取子数组中所有对象的数组。

计算将每个值映射到其长度的值的最大长度：

 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": "somethinglongest", "ref": "option3a" }, { "label": "Other", "ref": "option3b" } ] }; console.log(Math.max(...Object.values(obj).flat().map(o => o.label.length))); 

Answer 3

直截了当的方法：

 let 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"} ] }; let longest = 0 for (key in obj){ if (!obj.hasOwnProperty(key)) continue; for (let x of obj[key]){ if (x.label.length > longest) longest = x.label.length; } } console.log(longest); 

Answer 4

另一种选择是遍历obj对象的自身属性，并检查每个标签的长度是否长于先前的最长​​长度。

 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": "somethinglongest", "ref": "option3a" }, { "label": "Other", "ref": "option3b" } ] } let longest = 0; for (key in obj) { if(obj.hasOwnProperty(key)) { obj[key].forEach(item => { if (item.label.length > longest) longest = item.label.length; }) } } console.log(longest); 

Answer 5

您可以查找对象，然后查找所需的密钥。 这适用于任意深度的数据。

 function getLongest(object, key) { return Object.values(object).reduce((l, v) => { if (key in v) return Math.max(l, v[key].length); if (v && typeof v === 'object') return Math.max(l, getLongest(v, key)); return l; }, 0); } var 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" }] }; console.log(getLongest(data, 'label')); 

Answer 6

您可以使用此1行语句。

let maxLen = Math.max(...Object.keys(obj).map((key) => Math.max(...obj[key].map((o) => o.label.length))));

节点REPL上的示例

> 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": "somethinglongest",
.....           "ref": "option3a"
.....         },
...         {
.....           "label": "Other",
.....           "ref": "option3b"
.....         }
...       ]
...     }
undefined
>
> Math.max(...Object.keys(obj).map((key) => Math.max(...obj[key].map((o) => o.label.length))))
16
>

详细概述

let keys = Object.keys(obj);

let maxLens = keys.map((key) => {
    let arr = obj[key];
    return Math.max(...arr.map((o) => o.label.length))
});

let max = Math.max(...maxLens);

console.log(keys);    // [ 'array1', 'array2' ]
console.log(maxLens); // [ 10, 16 ]
console.log(max);     // 16

以下是帮助您的示例。

> Math.max(4, 5, 7)
7
>
> Math.max([4, 5, 7])
NaN
>
> Math.max(...[6, 7])
7
>
> let a = [2, 4, 5]
undefined
>
> a2 = a.map((num) => num ** 2)
[ 4, 16, 25 ]
>
> a3 = a.map((num) => num + 2)
[ 4, 6, 7 ]
>