Class Records Summary

class_records_summary.js

const EXAM_WEIGHT     = 0.65;
const EXERCISE_WEIGHT = 0.35;

const generateClassRecordSummary = students => {
  let studentGrades = generateStudentGrades(students);
  let examSummaries = generateExamSummaries(students);

  return { studentGrades: studentGrades, exams: examSummaries };
};

const generateStudentGrades = students => {
  return Object.keys(students).map(student => {
    let examScoresAvg     = findAvg(students[student].scores.exams);
    let exerciseScoresSum = findSum(students[student].scores.exercises)
    let percentGrade      = findPercentGrade(examScoresAvg, exerciseScoresSum);
    let letterGrade       = findLetterGrade(percentGrade);

    return `${percentGrade} (${letterGrade})`;
  });
};

const generateExamSummaries = students => {
  let examScoresByStudent = extractExamScores(students);

  return examScoresByStudent[0].map((_, studentNum) => {
    let examScoresByExam = findExamScoresByExam(examScoresByStudent, studentNum);
    let avg              = findAvg(examScoresByExam);
    let [min, max]       = findMinMax(examScoresByExam);

    return { average: avg, minimum: min, maximum: max };
  });
};

const extractExamScores = students => {
  return Object.keys(students).map(student => students[student].scores.exams);
};

const findExamScoresByExam = (examScoresByStudent, studentNum) => {
  return examScoresByStudent.map(exam => exam[studentNum]);
};

const findSum    = scores => scores.reduce((sum, score) => sum + score, 0);
const findAvg    = scores => findSum(scores) / scores.length;
const findMinMax = scores => [Math.min(...scores), Math.max(...scores)];

const findPercentGrade = (examScoresAvg, exerciseScoresSum) => {
  return Math.round(examScoresAvg * EXAM_WEIGHT + exerciseScoresSum * EXERCISE_WEIGHT);
};

const findLetterGrade = score => {
  if      (score >= 93) return 'A';
  else if (score >= 85) return 'B';
  else if (score >= 77) return 'C';
  else if (score >= 69) return 'D';
  else if (score >= 60) return 'E';
  else                  return 'F';
};