Ranking the users based on percentage using map/filter/reduce

Question

I want to display all the details of the users based on their percentage of marks and assign ranks to them. Here I'm getting all the details. How to sort and print the users like.

Tom has scored marks in Science - 80 Maths - 89 English - 91 and secured 86.67 % and his rank is 1.  

Similarly every user in the students object.

var students = [{
  name: "John",
  age: 20,
  id: 1,
  marks: {
    science: 80,
    maths: 90,
    english: 67
  }
}, {
  name: "Jack",
  age: 22,
  id: 3,
  marks: {
    science: 56,
    maths: 91,
    english: 81
  }
}, {
  name: "Robert",
  age: 23,
  id: 2,
  marks: {
    science: 75,
    maths: 79,
    english: 87
  }
}, {
  name: "Tom",
  age: 20,
  id: 4,
  marks: {
    science: 80,
    maths: 89,
    english: 91
  }
}];


var inDetail = getPercentageAndRank(students);

function getPercentageAndRank(students) {

  var details = students.map(function(getMarks) {
    console.log(((getMarks.marks.english + getMarks.marks.maths + getMarks.marks.science) / 3));
    return {
      name: getMarks.name,
      science: getMarks.marks.science,
      maths: getMarks.marks.maths,
      english: getMarks.marks.english,
      percentage: ((getMarks.marks.english + getMarks.marks.maths + getMarks.marks.science) / 3)
    };
  })

  return details.map(function(gg) {
    return [
      gg.name,
      "has scored marks in Science -",
      gg.science,
      "Maths -",
      gg.maths,
      "English -",
      gg.english,
      "and secured", (gg.percentage).toFixed(2),
      "%."
    ].join(' ');

  });
}

Output:

["John has scored marks in Science - 80 Maths - 90 English - 67 and secured 79.00 %.",
    "Jack has scored marks in Science - 56 Maths - 91 English - 81 and secured 76.00 %.",
    "Robert has scored marks in Science - 75 Maths - 79 English - 87 and secured 80.33 %.",
    "Tom has scored marks in Science - 80 Maths - 89 English - 91 and secured 86.67 %."]

Here the output I'm getting is not according to the above said. How can I get as above..

Answer 1

You need to add:

.sort(function(a, b) {
    return b.percentage - a.percentage;
  });

Check this solution.

var students = [{
  name: "John",
  age: 20,
  id: 1,
  marks: {
    science: 80,
    maths: 90,
    english: 67
  }
}, {
  name: "Jack",
  age: 22,
  id: 3,
  marks: {
    science: 56,
    maths: 91,
    english: 81
  }
}, {
  name: "Robert",
  age: 23,
  id: 2,
  marks: {
    science: 75,
    maths: 79,
    english: 87
  }
}, {
  name: "Tom",
  age: 20,
  id: 4,
  marks: {
    science: 80,
    maths: 89,
    english: 91
  }
}];


var inDetail = getPercentageAndRank(students);

function getPercentageAndRank(students) {

  var details = students.map(function(getMarks) {
    // console.log(((getMarks.marks.english + getMarks.marks.maths + getMarks.marks.science) / 3));
    return {
      name: getMarks.name,
      science: getMarks.marks.science,
      maths: getMarks.marks.maths,
      english: getMarks.marks.english,
      percentage: ((getMarks.marks.english + getMarks.marks.maths + getMarks.marks.science) / 3),
      rank: 0
    };
  }).sort(function(a, b) {
    return b.percentage - a.percentage;
  });

  for (var i = 0; i < details.length; i++) {
    // Updating the rank in order.
    details[i].rank = i + 1;
  }

  return details.map(function(gg) {
    return [
      gg.name,
      "has scored marks in Science -",
      gg.science,
      "Maths -",
      gg.maths,
      "English -",
      gg.english,
      "and secured", (gg.percentage).toFixed(2),
      "%", "and his rank is", gg.rank + "."
    ].join(' ');

  }).reduce(function(previous, current) {
    return previous + '\n' + current;
  }); // String result...
}
console.log(inDetail);

And in this question you don't need a filter function.