solution number 3

let solution = (relation) => {
  let answer = 0;
  let dataRow = [];
  let findDuplicates = (arr) =>
    arr.filter((item, index) => arr.indexOf(item) != index);

  //   - Uniqueness: The relation does not have two distinct tuples
  //  (i.e. rows or records in common database language)
  //   with the same values for these attributes.
  for (let i = 0; i < relation[0].length; i++) {
    const rowData = relation.map((data) => data[i]);
    const uniqueDuplicates = [...new Set(findDuplicates(rowData))];

    if (uniqueDuplicates.length === 0) {
      dataRow.push(i);
      answer++;
    }
  }

  // checking value in data array
  for (let i = 0; i < relation[0].length; i++) {
    for (let j = 0; j < relation[0].length; j++) {
      const isCurrUnique = dataRow.findIndex((dataCurr) => dataCurr === i) > -1;
      const isNextUnique = dataRow.findIndex((dataNext) => dataNext === j) > -1;

      // prevent same value
      if (i !== j) {
        if (!isCurrUnique && !isNextUnique) {
          const oneRows = relation.map((data) => `${data[i]} ${data[j]}`);
          const isDuplicatedCol = [...new Set(findDuplicates(oneRows))];

          if (isDuplicatedCol.length === 0) {
            dataRow.push(i);
            dataRow.push(j);
            answer++;
          }
        }
      }
    }
  }

  return answer;
};

// [Student number, Name, Major, Grade]
let relation = [
  ["100", "ryan", "music", "2"],
  ["200", "apeach", "math", "2"],
  ["300", "tube", "computer", "3"],
  ["400", "con", "computer", "4"],
  ["500", "muzi", "music", "3"],
  ["600", "apeach", "music", "2"],
];

// answer: 2

console.log(solution(relation));