获取数组对象中第一个对象的键

Question

我正在尝试从对象数组中获取一组（不同的）键。

arr =[
   {id: 1, desc: "", name: "", objectives: Array(3), …},
   {id: 2, desc: "", name: "", objectives: Array(3), …},
   {id: 3, desc: "", name: "", objectives: Array(3), …},
   {id: 4, desc: "", name: "", objectives: Array(3), …},
]

所需的输出是 [id, desc, name, targets]。我试过了：

Object.keys(arr)[0]
// output [{id: 1, desc: "", name: "", objectives: Array(3), …}]

arr.flatMap(Object.key)
// output ["id", "desc", "name", "objectives", "id", "desc", "name", "objectives", "id", "desc", "name", "objectives", "id", "desc", "name", "objectives"]

如果我在搜索 SO 时错过了这个问题的答案，我很抱歉。任何帮助将不胜感激。

Answer 1

这应该可行。

arr = [
   {id: 1, desc: "", name: "", objectives: Array(3)},
   {id: 2, desc: "", name: "", objectives: Array(3)},
   {id: 3, desc: "", name: "", objectives: Array(3)},
   {id: 4, desc: "", name: "", objectives: Array(3)},
];

keyArr = [];
Object.keys(arr).find(keys => {
    Object.keys(arr[keys]).find(key => {
    keyArr.push(key);
  });
})
console.log(keyArr);

Answer 2

    const arr =[
      {id: 1, desc: "", name: "", objectives: Array(3), …},
      {id: 2, desc: "", name: "", objectives: Array(3), …},
      {id: 3, desc: "", name: "", objectives: Array(3), …},
      {id: 4, desc: "", name: "", objectives: Array(3), …},
    ];

    let distinct = function(arr, key_name) {
       let seen_values = [];
       let unique_objects = [];
       for(i = 0; i < arr.length; i++) {
         // If this value is new, a.k.a. distinct then add it to our filtered list.
         if(!seen_values.includes(arr[i][key_name]) {
            unique_objects.push(arr[i])
         }
         // Add this value to our seen values.
         seen_values.push(arr[i][key_name])
       }
       return unique_objects;
    }

    // Example usage, filter by desc
    let filtered_set = distinct(arr, "desc")

    // Example usage, filter by id
    let filtered_set_2 = distinct(arr, "id")

所以这应该有效。 distinct 函数将通过给定的 key_name 过滤传入的 arr。这种方法的一个限制是，如果您的对象中的一个值是另一个对象，您将需要对该对象进行更深入的检查才能比较它们。

Answer 3

您可以使用Set 清除重复项：

const arr = [
   {id: 1, desc: "", name: "", objectives: []},
   {id: 2, desc: "", name: "", objectives: []},
   {id: 3, desc: "", name: "", objectives: []},
   {id: 4, desc: "", name: "", objectives: []},
];

const keys = [...new Set(arr.flatMap(Object.keys))];

console.log(keys);