Filter Array of objects based on repetitive values

Question

I am trying to populate an array of objects in the UI which has repetitive properties of title with teacher and students value.

Please find the original data -

const data = [
{
    id: "1",
    title: "Principle",
    name: "John Doe",
    children: [
    {
        id: "random id",
        title: "Teacher",
        name: "Clark Kent",
    },
    {
        id: "random id",
        title: "Teacher",
        name: "Bruce Wayne",
        children: [
        {
            id: "random id",
            title: "Student",
            name: "Jason Todd",
        },
        {
            id: "random id",
            title: "Student",
            name: "Dick Grayson",
        },
        {
            id: "random id",
            title: "Student",
            name: "Tim Drake",
        },
        {
            id: "random id",
            title: "Student",
            name: "Jason Todd",
        },
        {
            id: "random id",
            title: "Student",
            name: "Jason Todd",
        },
        {
            id: "random id",
            title: "Student",
            name: "Jason Todd",
        },
        {
            id: "random id",
            title: "Student",
            name: "Jason Todd",
        },
        ],
    },
    {
        id: "random id",
        title: "Teacher",
        name: "Clark Kent",
    },
    {
        id: "random id",
        title: "Teacher",
        name: "Barry Allen",
    },
    {
        id: "random id",
        title: "Teacher",
        name: "Clark Kent",
    },
    {
        id: "random id",
        title: "Teacher",
        name: "Clark Kent",
    },
    {
        id: "random id",
        title: "Teacher",
        name: "Clark Kent",
    },
    ],
},
];

which contains principal, teacher, and students. For eg., if the teacher name is repetitive and is coming like for eg., 5 times in data for Clark Kent, then I wish to restrict the data to show 3 entries and add one object, to specify that there are more entries with this name. like below -

  {
    id: "random id",
    title: "Teacher",
    name: "Clark Kent",
    more: true,
    remaining: 2,
  },

In the end, so my data can look like the below format to populate in UI -

const data = [
{
    id: "1",
    title: "Principle",
    name: "John Doe",
    children: [
    {
        id: "random id",
        title: "Teacher",
        name: "Clark Kent",
    },
    {
        id: "random id",
        title: "Teacher",
        name: "Bruce Wayne",
        children: [
        {
            id: "random id",
            title: "Student",
            name: "Jason Todd",
        },
        {
            id: "random id",
            title: "Student",
            name: "Dick Grayson",
        },
        {
            id: "random id",
            title: "Student",
            name: "Tim Drake",
        },
        {
            id: "random id",
            title: "Student",
            name: "Jason Todd",
        },
        {
            id: "random id",
            title: "Student",
            name: "Jason Todd",
        },
        {
            id: "random id",
            title: "Student",
            name: "Jason Todd",
            more: true,
            remaining: 2,
        },
        ],
    },
    {
        id: "random id",
        title: "Teacher",
        name: "Clark Kent",
    },
    {
        id: "random id",
        title: "Teacher",
        name: "Barry Allen",
    },
    {
        id: "random id",
        title: "Teacher",
        name: "Clark Kent",
    },
    {
        id: "random id",
        title: "Teacher",
        name: "Clark Kent",
        more: true,
        remaining: 2,
    },
    ],
},
];

Please help.

HI @PaoloTormon, the obj where more is added, will merge in UI as '+2 more Clark Kent' with + ${remaining} ${name}, Click to view more in UI, so we can keep Clark Kent as 2 — Akshay
– Akshay, Commented Sep 21, 2021 at 8:12

vsemozhebuty · Accepted Answer · 2021-09-21 23:47:20Z

Some assumptions:

id in "more" object is just copied from the first excessive person.
No children field is expected in excessive persons.

const data = [
  {
    id: '1',
    title: 'Principle',
    name: 'John Doe',
    children: [
      {
        id: 'random id',
        title: 'Teacher',
        name: 'Clark Kent',
      },
      {
        id: 'random id',
        title: 'Teacher',
        name: 'Bruce Wayne',
        children: [
          {
            id: 'random id',
            title: 'Student',
            name: 'Jason Todd',
          },
          {
            id: 'random id',
            title: 'Student',
            name: 'Dick Grayson',
          },
          {
            id: 'random id',
            title: 'Student',
            name: 'Tim Drake',
          },
          {
            id: 'random id',
            title: 'Student',
            name: 'Jason Todd',
          },
          {
            id: 'random id',
            title: 'Student',
            name: 'Jason Todd',
          },
          {
            id: 'random id',
            title: 'Student',
            name: 'Jason Todd',
          },
          {
            id: 'random id',
            title: 'Student',
            name: 'Jason Todd',
          },
        ],
      },
      {
        id: 'random id',
        title: 'Teacher',
        name: 'Clark Kent',
      },
      {
        id: 'random id',
        title: 'Teacher',
        name: 'Barry Allen',
      },
      {
        id: 'random id',
        title: 'Teacher',
        name: 'Clark Kent',
      },
      {
        id: 'random id',
        title: 'Teacher',
        name: 'Clark Kent',
      },
      {
        id: 'random id',
        title: 'Teacher',
        name: 'Clark Kent',
      },
    ],
  },
];

const result = reduceRepetitions(data, 'name', 3);
console.log(JSON.stringify(result, null, '  '));

function reduceRepetitions(array, checkKey, maxRepetitions) {
  const reduced = [];

  const counter = {};

  for (const person of array) {
    const checkValue = person[checkKey];
    counter[checkValue] ??= { count: 0, moreObject: null };
    counter[checkValue].count++;
    if (counter[checkValue].count <= maxRepetitions) {
      reduced.push({
        ...person,
        ...person.children ?
          { children: reduceRepetitions(person.children, checkKey, maxRepetitions) } :
          {},
      });
    } else if (!counter[checkValue].moreObject) {
      counter[checkValue].moreObject = { ...person, more: true, remaining: 1 };
      reduced.push(counter[checkValue].moreObject);
    } else {
      counter[checkValue].moreObject.remaining++;
    }
  }

  return reduced;
}

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