How to grouping data from array in js-CodePudding

I have an array with different objects where each object is an classes. Looks like this:

sessions = [
      { session_id: 1, time: '09:00', student: { student_id: 1, name: 'Adi' }, class: { class_id: 1, name: 'A' } },
      { session_id: 2, time: '10:00', student: { student_id: 7, name: 'Dede' }, class: { class_id: 4, name: 'D' } },
      { session_id: 1, time: '09:00', student: { student_id: 3, name: 'Bayu' }, class: { class_id: 2, name: 'B' } },
      { session_id: 1, time: '09:00', student: { student_id: 2, name: 'Budi' }, class: { class_id: 1, name: 'A' } },
      { session_id: 2, time: '10:00', student: { student_id: 3, name: 'Maha' }, class: { class_id: 3, name: 'C' } },
    ];

I want to change the data to be like this, (grouping by session_id or time):

sessions = [
   {
     session_id: 1,
     time: '09:00',
     classes: [
       {
         class_id: 1,
         name: 'A',
         students: [
           { student_id: 1, name: 'Adi' },
           { student_id: 1, name: 'Budi' },
         ],
       },
       {
         class_id: 2,
         name: 'B',
         students: [
           { student_id: 3, name: 'Bayu' },
         ],
       },
     ],
   },
   {
     session_id: 2,
     time: '10:00',
     classes: [
       {
         class_id: 3,
         name: 'C',
         students: [
           { student_id: 6, name: 'Maha' },
         ],
       },
       {
         class_id: 4,
         name: 'D',
         students: [
           { student_id: 7, name: 'Dede' },
         ],
       },
     ],
   },
  ];

I'm tired of trying to solve it, because my javascript isn't that great. please help me to solve the code.

CodePudding user response：

You can use lodash.groupBy. For example:

const sessions = [
    { session_id: 1, time: '09:00', student: { student_id: 1, name: 'Adi' }, class: { class_id: 1, name: 'A' } },
    { session_id: 2, time: '10:00', student: { student_id: 7, name: 'Dede' }, class: { class_id: 4, name: 'D' } },
    { session_id: 1, time: '09:00', student: { student_id: 3, name: 'Bayu' }, class: { class_id: 2, name: 'B' } },
    { session_id: 1, time: '09:00', student: { student_id: 2, name: 'Budi' }, class: { class_id: 1, name: 'A' } },
    { session_id: 2, time: '10:00', student: { student_id: 3, name: 'Maha' }, class: { class_id: 3, name: 'C' } },
];
const result = Object.entries(_.groupBy(sessions, 'session_id')).map(session => ({ session_id: Number(session[0]), time: session[1][0].time, classes: Object.entries(_.groupBy(session[1], s => s.class.class_id)).map(c => ({ class_id: Number(c[0]), name: c[1][0].class.name, students: c[1].map(x => ({ student_id: x.student.student_id, name: x.student.name })) })) }))
console.log(result)

<script src="https://cdn.jsdelivr.net/npm/[email protected]/lodash.min.js"></script>

CodePudding user response：

Try below snippet:

const sessions = [
      { session_id: 1, time: '09:00', student: { student_id: 1, name: 'Adi' }, class: { class_id: 1, name: 'A' } },
      { session_id: 2, time: '10:00', student: { student_id: 7, name: 'Dede' }, class: { class_id: 4, name: 'D' } },
      { session_id: 1, time: '09:00', student: { student_id: 3, name: 'Bayu' }, class: { class_id: 2, name: 'B' } },
      { session_id: 1, time: '09:00', student: { student_id: 2, name: 'Budi' }, class: { class_id: 1, name: 'A' } },
      { session_id: 2, time: '10:00', student: { student_id: 3, name: 'Maha' }, class: { class_id: 3, name: 'C' } },
    ];

const newSessions = sessions.reduce((acc, session)=> {
    const sessionIndex = acc.findIndex(item => item.session_id == session.session_id);
    if(sessionIndex > -1){
        updateSessionClasses(acc[sessionIndex], session)
    }else {
        acc.push({ session_id: session.session_id, time: session.time, classes: [{...session.class, students: [session.student]}]  })
    };
    return acc;
}, []);

function updateSessionClasses(storedSession, session){
    const classIndex = storedSession.classes.findIndex(c => c.class_id == session.class.class_id);
    if(classIndex > -1){
      storedSession.classes[classIndex].students.push(session.student)
    }else {
       storedSession.classes.push({...session.class, students: [session.student]}) 
    }
}

console.log(newSessions)