计算一个值在嵌套对象的多级数组中出现的次数

Question

So I've got an array objects that contains the startDate , endDate and an array of student objects which contains the student's fullName , docId and attendanceStatus for a course for a class. I'm not allowed to change the way the data is structured.

[
   {
     startDate: Mon Jul 26 2021 08:19:00 GMT+0800 (Philippine Standard Time),
     endDate: Mon Jul 26 2021 09:19:00 GMT+0800 (Philippine Standard Time),
     id: "EE201_433",
     title: "EE201",
     students: [
      {docId: "LKfpyWyWuXlbBLUBoRp2", attendanceStatus: "Present", fullName: "John Smith"},
      {docId: "nwHWP3iNjGm2tEODsaLo", attendanceStatus: "Absent", fullName: "Claire Smith"},
      {docId: "x9TLXbsVfgpZfQU7aj8Z", attendanceStatus: "Excused", fullName: "Jane Smith"}
     ]
   },
   {
     startDate: Mon Jul 19 2021 08:19:00 GMT+0800 (Philippine Standard Time),
     endDate: Mon Jul 19 2021 09:19:00 GMT+0800 (Philippine Standard Time),
     id: "EE201_432",
     title: "EE201",
     students: [
      {docId: "LKfpyWyWuXlbBLUBoRp2", attendanceStatus: "Absent", fullName: "John Smith"},
      {docId: "nwHWP3iNjGm2tEODsaLo", attendanceStatus: "Present", fullName: "Claire Smith"},
      {docId: "x9TLXbsVfgpZfQU7aj8Z", attendanceStatus: "Excused", fullName: "Jane Smith"}
     ]
   }
]

How can I create a function that takes the student's docId as an argument then returns something like this. How can I count how many times a student is absent, present or excused?

{
 LKfpyWyWuXlbBLUBoRp2: {present: 1, absent: 1, excused: 0},
}

Answer 1

I don't know if this is the best way to do this but this works

 const courses = [ { startDate: "Mon Jul 26 2021 08:19:00 GMT+0800 (Philippine Standard Time)", endDate: "Mon Jul 26 2021 09:19:00 GMT+0800 (Philippine Standard Time)", id: "EE201_433", title: "EE201", students: [ {docId: "LKfpyWyWuXlbBLUBoRp2", attendanceStatus: "Present", fullName: "John Smith"}, {docId: "nwHWP3iNjGm2tEODsaLo", attendanceStatus: "Absent", fullName: "Claire Smith"}, {docId: "x9TLXbsVfgpZfQU7aj8Z", attendanceStatus: "Excused", fullName: "Jane Smith"} ] }, { startDate: "Mon Jul 19 2021 08:19:00 GMT+0800 (Philippine Standard Time)", endDate: "Mon Jul 19 2021 09:19:00 GMT+0800 (Philippine Standard Time)", id: "EE201_432", title: "EE201", students: [ {docId: "LKfpyWyWuXlbBLUBoRp2", attendanceStatus: "Absent", fullName: "John Smith"}, {docId: "nwHWP3iNjGm2tEODsaLo", attendanceStatus: "Present", fullName: "Claire Smith"}, {docId: "x9TLXbsVfgpZfQU7aj8Z", attendanceStatus: "Excused", fullName: "Jane Smith"} ] }, ] const id = "LKfpyWyWuXlbBLUBoRp2"; const getStudentAttendance = (id) => { let student = { absent: 0, present: 0, excused: 0 } courses.forEach(course => { const { attendanceStatus } = course.students.find(({ docId }) => docId === id) if (attendanceStatus) { student[attendanceStatus.toLowerCase()] += 1 } }) return { [id]: student } } console.log(getStudentAttendance(id))

Answer 2

 document.getElementById("btn").addEventListener('click', () => { const data = [ { startDate: "Mon Jul 26 2021 08:19:00 GMT+0800 (Philippine Standard Time)", endDate: "Mon Jul 26 2021 09:19:00 GMT+0800 (Philippine Standard Time)", id: "EE201_433", title: "EE201", students: [ {docId: "LKfpyWyWuXlbBLUBoRp2", attendanceStatus: "Present", fullName: "John Smith"}, {docId: "nwHWP3iNjGm2tEODsaLo", attendanceStatus: "Absent", fullName: "Claire Smith"}, {docId: "x9TLXbsVfgpZfQU7aj8Z", attendanceStatus: "Excused", fullName: "Jane Smith"} ] }, { startDate: "Mon Jul 19 2021 08:19:00 GMT+0800 (Philippine Standard Time)", endDate: "Mon Jul 19 2021 09:19:00 GMT+0800 (Philippine Standard Time)", id: "EE201_432", title: "EE201", students: [ {docId: "LKfpyWyWuXlbBLUBoRp2", attendanceStatus: "Absent", fullName: "John Smith"}, {docId: "nwHWP3iNjGm2tEODsaLo", attendanceStatus: "Present", fullName: "Claire Smith"}, {docId: "x9TLXbsVfgpZfQU7aj8Z", attendanceStatus: "Excused", fullName: "Jane Smith"} ] }, ] var present = 0; var absent = 0; var excused = 0; var id = document.getElementById('id').value; for (var A = 0; A < data.length; A++){ for(var B = 0; B < data[A].students.length; B++){ var attendance = data[A].students[B].attendanceStatus if(data[A].students[B].docId == id){ if(attendance == 'Present'){present++} else if(attendance == 'Absent'){absent++} else{excused++} } } } var node = document.createElement("LI"); var textnode = document.createTextNode(id + ': ' + ' present: ' + present + ', absent: ' + absent + ', excused: ' + excused); node.appendChild(textnode); document.getElementById("list").appendChild(node); })

 <label>Enter ID</label> <input id="id"> <button id="btn">Get attendance</button> <ul id="list"></ul>