Array.forEach总是返回undefined，所以result总是undefined。如果您在操作后查看input，它确实包含您指定的详细信息。
或者，如果您打算保持input不变，可以将input扩展到一个名为result的新数组中，并在result上执行循环。

const input = 
[
    {
        "country": { "id": 87745195, "action": "Analyze" },
        "states": [
            { "id": 83589582, "action": "Verify" },
            { "id": 87335656, "action": "Analyze" }
        ]
    },
    {
        "country": { "id": 83861166, "action": "Verify" },
        "states": [
            { "id": 82175746, "action": "Closed" },
            { "id": 78745158, "action": "Closed" }
        ]
    }
]

const details = { "totalOpenRadars": 1, "totalClosedRadars": 1 }

const id = 82175746

input.forEach((element) => {
    element.states.forEach((state) => {
        if(state.id === id) {
            state.details = details
        }

    });
});
console.log(input);

字符串

您可以使用Array.prototype.map()：

const input = [{"country": { "id": 87745195, "action": "Analyze" },"states": [{ "id": 83589582, "action": "Verify" },{ "id": 87335656, "action": "Analyze" }]},{"country": { "id": 83861166, "action": "Verify" },"states": [{ "id": 82175746, "action": "Closed" },{ "id": 78745158, "action": "Closed" }]}]
const details = { "totalOpenRadars": 1, "totalClosedRadars": 1 }
const id = 82175746

const result = input.map(item => item.states.map(state => ({
  ...state,
  ...(state.id === id ? { details } : {})
})))

console.log(result)

字符串

这应该是做它

const appendDetails = (data, id, details) => 
  data.map(d => {
    return {
      ...d,
      states: d.states.map(s => {
        if(s.id !== id){
          return s
        }
        return {
          ...s,
          details
        }
      })
    } 
  })

const input = 
[
    {
        "country": { "id": 87745195, "action": "Analyze" },
        "states": [
            { "id": 83589582, "action": "Verify" },
            { "id": 87335656, "action": "Analyze" }
        ]
    },
    {
        "country": { "id": 83861166, "action": "Verify" },
        "states": [
            { "id": 82175746, "action": "Closed" },
            { "id": 78745158, "action": "Closed" }
        ]
    }
]

const details = { "totalOpenRadars": 1, "totalClosedRadars": 1 }

const id = 82175746

console.log(appendDetails(input, id, details))

字符串

可重用的方法不仅仅是键或值，每个可能的元素都以整洁干净的方式呈现。
你可以改变数组，对象的键在哪里查找，键在哪里要与值匹配，以及新的键和新的值。

const students = [
    {
      "name": "Amoos",
      "skills": [
        { id: 11, name: "html" },
        { id: 12, name: "css" }
      ],
      "sports": [
        {id: 31, name: "football"},
        {id: 32, name: "circket"},
      ]
    },
    {
      "name": "Rifat",
      "skills": [
        { id: 21, name: "reactjs" },
        { id: 22, name: "nextjs" }
      ],
      "sports": [
        {id: 41, name: "baseball"},
        {id: 42, name: "volleyball"},
      ]
    },
]

 

const addNewValueByKeyInArray = (arrayData, where, key, value, newKey, newValue ) => {
   return arrayData.map(( d ) => d[where].map((w) => (w[key] === value) ? {
            ...w, [newKey]: newValue
        } : {...w}
    ))
}

// EXAMPL #1
console.log(addNewValueByKeyInArray(students, 'sports', 'id', 42, 'details', { 'region': 'worldwide', 'first_played': '1895' }));

// EXAMPL #2
console.log(addNewValueByKeyInArray(students, 'skills', 'id', 22, 'details', { 'author': 'Guillermo Rauch', 'first_version': '2016' }));

字符串