如何从值列表中获取键？

Question

我想根据给定的值列表获取键..

这是我要找的，

这是我的对象，

my_obj = {
  "A": "a_id",
  "B": "b_id",
  "C": "c_id",
  "D": "d_id",
  "E": "status",
  "F": "start_time",
  "G": "end_time",
  "H": "count",
  "I": "task_desc",
  "J": "approved",
  "K": "point",
  "L": "complex",
  "M": "c_date",
  "N": "final_date"
}
my_val = ['c_date', 'final_date', 'my_due_date', 'start_date']

所以，从上面my_val我想得到，["M", "N"]

我尝试使用下划线 invert 来反转我的对象以获取...一切都很好，除了 return 键而不是值..

这是我尝试过的，

my_obj = {
  "A": "a_id",
  "B": "b_id",
  "C": "c_id",
  "D": "d_id",
  "E": "status",
  "F": "start_time",
  "G": "end_time",
  "H": "count",
  "I": "task_desc",
  "J": "approved",
  "K": "point",
  "L": "complex",
  "M": "c_date",
  "N": "final_date"
}
my_val = ['c_date', 'final_date', 'my_due_date', 'start_date']
out = _.filter(my_val, function(v) { return _.invert(my_obj)[v]})
console.log(out)

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js"></script>

_.invert(my_obj)[v]  - this gives me a `key` but inside filter didnt..

我的代码有什么问题？如何得到它？

Answer 1

这应该适合你

my_obj = {
      "A": "a_id",
      "B": "b_id",
      "C": "c_id",
      "D": "d_id",
      "E": "status",
      "F": "start_time",
      "G": "end_time",
      "H": "count",
      "I": "task_desc",
      "J": "approved",
      "K": "point",
      "L": "complex",
      "M": "c_date",
      "N": "final_date"
    }

my_val = ['c_date', 'final_date', 'my_due_date', 'start_date']

var output = [];

for (var i = 0; i < my_val.length; i++) {
  for (var key in my_obj) {
    if (my_obj[key] === my_val[i]) {
      output.push(key);
    }
  }
}

console.log(output);

Answer 2

如果您只想要键的子集：

let subset = Object.keys(my_obj).filter((key, _) =>
  my_val.includes(my_obj[key])
);

Answer 3

my_obj = {
  "A": "a_id",
  "B": "b_id",
  "C": "c_id",
  "D": "d_id",
  "E": "status",
  "F": "start_time",
  "G": "end_time",
  "H": "count",
  "I": "task_desc",
  "J": "approved",
  "K": "point",
  "L": "complex",
  "M": "c_date",
  "N": "final_date"
}
let my_val = ['c_date', 'final_date', 'my_due_date', 'start_date']
let result = [];

for (let key in my_obj)
{
  for (let i = 0; i < my_val.length; i++)
  {
    if (my_obj[key] == my_val[i])
    {
      result.push(key);
    }
  }

}

console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js"></script>

Answer 4

您使用 filter() 不正确。该方法需要回调函数 return 一个布尔值，但这里你 return 一个字符串。如果你想为 my_val 中的每个条目 return 一个字符串（键），你应该使用 map() 代替。

Answer 5

可以用Object.keys得到一个键数组，根据每个键对应的值是否包含在my_val数组中进行过滤； Array.prototype.includes() 确定数组是否包含某个元素和returns一个布尔值，非常适合filter:

my_obj = {
  "A": "a_id",
  "B": "b_id",
  "C": "c_id",
  "D": "d_id",
  "E": "status",
  "F": "start_time",
  "G": "end_time",
  "H": "count",
  "I": "task_desc",
  "J": "approved",
  "K": "point",
  "L": "complex",
  "M": "c_date",
  "N": "final_date"
}
my_val = ['c_date', 'final_date', 'my_due_date', 'start_date']

console.log(
  Object.keys(my_obj).filter(k => my_val.includes(my_obj[k]))
)

如何从值列表中获取键？

How can I get keys from list of values?

javascript

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underscore.js