如何使用数组函数获取数组的所有键和值

Question

Using this array

const university = [
  { Students: 4, Lecturers: 15, Faculty: 'Mathematics' },
  { Students: 4, Lecturers: 15, Faculty: 'English' },
  { Students: 4, Lecturers: 15, Faculty: 'Science'} 
] 

I want to return all values with a certain key:

const students = [
  { Students: 4 },
  { Students: 4 },
  { Students: 4 }
] 

I know I can do this with a for in loop:

for (const property in object) {
  console.log(`${property}: ${object[property]}`);
}

Is there anyway to achieve this with map , filter , find or reduce ? I can not seem to get the key out

Answer:

university.map(data => `Students: ${data.Students}`);

You could extract to a function.

getByKey(arr, val) {
    arr.map(data => `${val}: ${data[val]}`);
}


getKey(university, Faculty)

Answer 1

You can make use of map and inside map you can pass keys in array(which you want to pick) and take fromEntries to form the object.

 const university = [ { Students: 4, Lecturers: 15, Faculty: 'Mathematics' }, { Students: 4,Lecturers: 15, Faculty: 'English'} , { Students: 4, Lecturers: 15, Faculty: 'Science' } ]; const getGivenKeys=(arr,keys)=> arr.map(o=>Object.fromEntries(keys.map(k=>[k,o[k]]))); console.log(getGivenKeys(university, ['Students', 'Faculty'])); console.log(getGivenKeys(university, ['Students']));

Answer 2

Your key in that case is Students. So, you can do a map and return a new object with just that key.

 const university = [{ Students: 46, Lecturers: 2, Faculty: 'Mathematics' }, { Students: 65, Lecturers: 6, Faculty: 'English' }, { Students: 48, Lecturers: 4, Faculty: 'Science' }] let result = []; result = university.map(obj => { return { Students: obj.Students } }); console.log(result)

Answer 3

You can use map() with a clean solution:

const students = university.map(function(r){
    return {"Students" : r.Students};
});

Answer 4

使用map函数，但没有return关键字：

university.map(uni=>({Students:uni.Students}));