ES6 returning object with values from two arrays

Question

Self teaching myself development/ES6 and having some trouble with this question I’ve been trying to work through for a little while now.

I have grades of students, and the grade threshold. Trying to return an array that contains the student’s name, place in the array, and their score converted into a letter grade.

I have the switch statement, I’m just struggling with how to use it to return an object with student name, index in the array, and letter grade, as well as how to do this with the const and fat arrow syntax.

Any help/guidance would be appreciated.

Thanks

const scoreGrades = {
  A: 100,
  B: 90,
  C: 80,
  D: 70,
  F: 60,
}

const gradeReport = [{
  name: ‘Abby’,
  mark: 20,
}, {
  name: ‘Brian’,
  mark: 100,
}, {
  name: ‘Chella’,
  mark: 60
}];



const studentResults = (gradeReport, scoreGrades) => {

function getstudentMarks (result) {

  var mark = "";

  switch(true) {
    case mark < 60: 
      grade = "F";
      break;
    case mark < 70: 
      grade = "D";
      break;
    case mark < 80: 
      grade = "C";
      break;
    case mark < 90: 
      grade = "B";
      break;
    case mark <= 100:
      grade = "A";
      break;
  }


  return mark;
}


var i = 1;
while(i > 0 && <= 100){
  console.log(i, 'should be', getstudentMarks(i));
  i += 5;
}





}

"return an array that contains the student’s name, place in the array, and their score converted into a letter grade." This sounds like it would be more properly returned as an object, not an array. — Code-Apprentice
– Code-Apprentice, Commented Aug 11, 2018 at 16:56
@Code-Apprentice yes, you're right, that's what i meant (as indicated in the title), i've edited to show this, thanks — satoshinakamoto
– satoshinakamoto, Commented Aug 11, 2018 at 16:58

pawel · Accepted Answer · 2018-08-11 17:25:28Z

1

I suggest you use map method: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map.

Also, switch doesn't work like that. In a simplest implementation you could just use a series of if/else ifs.

Here's a working example:

function getGrade(mark) {
  if (mark < 60) {
    return "E";
  } else if (mark < 70) {
    return "D";
  } else if (mark < 80) {
    return "C";
  } else if (mark < 90) {
    return "B";
  } else {
    return "A";
  }
}

function getResults(scores) {
  return scores.map((score, index) => ({
    index: index,
    name: score.name,
    grade: getGrade(score.mark)
  }));
}

const studentScores = [{
  name: 'Abby',
  mark: 20,
}, {
  name: 'Brian',
  mark: 100,
}, {
  name: 'Chella',
  mark: 60
}];

console.log(getResults(studentScores));

The result is:

[
    {"index":0,"name":"Abby","grade":"E"}, 
    {"index":1,"name":"Brian","grade":"A"}, 
    {"index":2,"name":"Chella","grade":"D"}
]

answered Aug 11, 2018 at 17:25

pawel

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1 Comment

satoshinakamoto Over a year ago

thanks for this, very helpful! reading over the article makes it a lot more clear why the map method is a good choice.

tofu head · Accepted Answer · 2018-08-11 17:41:34Z

const scoreGrades = {
A: 100,
B: 90,
C: 80,
D: 70,
F: 60,
}

const gradeReport = [{
  name: 'Abby',
  mark: 20,
}, {
  name: 'Brian',
  mark: 100,
}, {
  name: 'Chella',
  mark: 60
}];



const getStudentResults = (gradeReport, scoreGrades) => {
  let studentResults = []
  gradeReport.forEach(student=>{
      let grade;

      if (student.mark >= 90) {
        grade = 'A';
      } else if (student.mark >= 80) {
        grade = 'B';
      } else if (student.mark >= 70) {
        grade = 'C';
      } else if (student.mark >= 60) {
        grade = 'D';
      } else {
          grade = 'F'
      } 

      studentResults.push({name:student.name, grade:grade});
  })

  return studentResults;
}

const studentResults = getStudentResults(gradeReport, scoreGrades);

console.log(studentResults);

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