通过与另一个对象（JavaScript）比较，有条件地向JSON对象添加新属性

Question

For example I have two arrays "StudentInfo"

[
  {
   "id": "1234",
   "name": "A"
  },
  {
   "id": "1134",
   "name": "B"
  },
  {
   "id": "2234",
   "name": "C"
  },
  {
   "id": "3234",
   "name": "D"
  }     
]

and "GoodStudentList"

[
  "1234",
  "1134"
]

So how could I add one more attribute about type of Student to StudentInfo depends on the GoodStudentList, if they have their ID in good list then their type is good, otherwise their type is Normal:

 [
      {
       "id": "1234",
       "name": "A",
       "type": "Good"
      },
      {
       "id": "1134",
       "name": "B"
       "type": "Good"
      },
      {
       "id": "2234",
       "name": "C"
       "type": "Normal"
      },
      {
       "id": "3234",
       "name": "D",
       "type": "Normal"
      }     
]

Sorry I know this maybe easy but I really can't understand about mapping thing in JS qwq

Answer 1

You can use forEach() to loop through the students array and test whether each id is in the good list with includes() . Then add the correct property depending on the result as you loop through students:

 let StudentInfo = [{"id": "1234","name": "A"},{"id": "1134","name": "B"},{"id": "2234","name": "C"},{"id": "3234","name": "D"} ] let GoodStudentList = ["1234","1134"] StudentInfo.forEach(student => { student.type = GoodStudentList.includes(student.id) ? "Good" : "Normal" }) console.log(StudentInfo) 

Answer 2

You could use the map method on the StudentInfo array, and for each element, check if that object's id exists in the GoodStudentList . It could look something like this:

StudentInfo = StudentInfo.map((student) => {
  if (GoodStudentList.indexOf(student.id) >= 0) {
   student.type = 'Good';
  } else {
    student.type = 'Normal';
  }
}) 

Here, you're checking if the index of the student id is greater than 0 for each student (meaning that it exists in the array). If if it doesn't exist in the array, it will return -1 and thus not pass the condition. Returned is the StudentInfo array with all students modified to now include the type property.

Answer 3

Using plain old iterations:

 let list = [ { "id": "1234", "name": "A" }, { "id": "1134", "name": "B" }, { "id": "2234", "name": "C" }, { "id": "3234", "name": "D" } ]; let good = [ "1234", "1134" ]; for (let key in list){ for (let i of good){ if (i === list[key].id){ list[key].type = "Good"; break; } else list[key].type = "Neutral"; } } console.log(list);