grads

const Grad = (data) => {
    dataCopy = JSON.parse(JSON.stringify(data))
    let gradesNamed =  dataCopy.grades.map(el => {
        if(!el.studentName){
            el['studentName'] = dataCopy.students.find(obj => obj.id === el.studentId).name;
        }
        if(!el.studentId){
            el['studentId'] = dataCopy.students.find(obj =>obj.studentName === el.name).id
        }
        return el
    })

    let examsNamed = dataCopy.exams.map(el => {
        if(!el.studentName){
            el['studentName'] = dataCopy.students.find(obj => obj.id === el.studentId).name

        }
        if(!el.studentId){
            el['studentId'] = dataCopy.students.find(obj =>obj.studentName === el.name).id
        }
        return el
    })

    let allStudents = dataCopy.students.map(el => {
        let elAvgGrade = gradesNamed.filter(obj => obj.studentName === el.name)
        .reduce((acc,obj1,_,array) => {
            acc = acc+ obj1.grade/array.length
            return acc
         },0 )

        let elAvgGradeExams = examsNamed.filter(obj => obj.studentName === el.name)
        .reduce((acc,obj1,_,array) => {
            acc =acc + obj1.grade/array.length
            return acc} ,0 )
        let totalGrade = 40*elAvgGrade/100 + 60*elAvgGradeExams/100

        let examsTaken = examsNamed.filter(obj => obj.studentName === el.name).length

        return {
            'id': el.id,
            'name': el.name,
            'grade': Number(totalGrade.toFixed(1)),
            'examsTaken': examsTaken
        }
    })

    let graduates = allStudents.filter(el =>{
        if( el.grade >= dataCopy.passingGrade && el.examsTaken >=2){
            return true
        } else {
            return false
        }
    })
    .map(el => {
        delete el.examsTaken
        return el
    })

    let nonGraduates = allStudents.filter(el => {
        if (el.grade < dataCopy.passingGrade || el.examsTaken < 2){
            return true
        } else {
            return false
        }
    })
    .map(el => {
        let reason = '';
        if (el.grade < dataCopy.passingGrade && el.examsTaken >= 2){
            reason = 'score'
        } else if (el.grade >= dataCopy.passingGrade && el.examsTaken < 2){
            reason = 'exams'
        } else if (el.grade < dataCopy.passingGrade && el.examsTaken < 2){
            reason = 'score and exams'
        }
        el['reason'] = reason
        delete el.grade
        delete el.examsTaken
        return el;
    })
    return {
        'course': dataCopy.course,
        'graduates': graduates,
        'nonGraduates': nonGraduates
    }

  }