JavaScript program that displays a list of names according to the Subject group-CodePudding

let a = 
[
    {
        Name: 'Josh',
        Subject: ['Biology', 'Chemistry'],  
    },
    {
        Name: 'James',
        Subject: ['Chemistry', 'Physics'],
    },
    {
        Name: 'Mary',
        Subject: ['Physics', 'Mathematics'],
    },
]

const result = a.reduce((groupedSubject, person) => {
    const Subject = person.Subject
    if(groupedSubject[Subject]== null) groupedSubject[Subject] = []
    groupedSubject[Subject].push(person)
    return groupedSubject
}, {})
    console.log(result)

I was able to group according to the subject, but subject is an array. how do i group it by individual subjects?

CodePudding user response：

You need to iterate Sports array as well.

const
    data = [{ Name: 'Ravindra', Sports: ['Chess', 'Cricket'] }, { Name: 'Ravi', Sports: ['Cricket', 'Football'] }, { Name: 'Rishabh', Sports: ['Table-Tennis', 'Football'] }],
    result = data.reduce((groupedSports, person) => {
        person.Sports.forEach(sport => {
            groupedSports[sport] ??= [];
            groupedSports[sport].push(person.Name);
        })
        return groupedSports;
    }, {});

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

CodePudding user response：

You can iterate over all sports and check if it already exists, if not, spread all current entries and add the new persons Name to the array.

let a = [{
    Name: 'Ravindra',
    Sports: ['Chess', 'Cricket'],
  },
  {
    Name: 'Ravi',
    Sports: ['Cricket', 'Football'],
  },
  {
    Name: 'Rishabh',
    Sports: ['Table-Tennis', 'Football'],
  },
]

const result = a.reduce((groupedSports, person) => {
  person.Sports.forEach((sport) => {
    groupedSports[sport] = groupedSports?.[sport]
      ? [...groupedSports[sport], person.Name]
      : [person.Name];
  });
  return groupedSports;
}, {});

console.log(result)