What is the best way to calculate the average grade for each student in an array that contains objects with exam submission data?

Question

What is the best way to calculate the average grade for each student in an array that contains objects with exam submission data?

Imagine having a collection of objects that hold details about exams submitted over a period. Here is the structure:

[
    { name: 'Freddy', grade: 10, date: '20/07/2022' },
    { name: 'Jose', grade: 8, date:'20/07/2022' },
    { name: 'Freddy, grade: 8', date: '25/07/2022' },
    { name: 'Daniel', grade: 5, date: '21/07/2022' },
    { name: 'Jose', grade: 5 }, date: '22/07/22',
  ]

The goal is to disregard the dates and compute the average grade for each student, resulting in a simple array like this:

[9, 6.5, 5]

In addition, if there's a need to reorder the array to match the sequence Freddy -> Jose -> Daniel, how can that be achieved?

While it may seem unusual, this specific order is necessary for later use as a dataset in Chart.js.

javascript arrays object

Answer 1

Answer №1

In order to achieve this:

I opted to utilize the `reduce` method to construct a dictionary containing the sum of grades and grade count for each student.
- Choosing a dictionary was strategic as it facilitates easy navigation while `reduce` processes through the array.
Subsequently, I employed `Object.keys()` to extract an array of keys from the dictionary and then used `map` to convert this array into objects representing each student's average grade.
- This approach was selected based on the notion that the resulting output could prove beneficial. While it may have been more straightforward to iterate over the dictionary directly and transform it into a collection of average values, I found this method preferable.
We proceeded to use `map` to isolate and retrieve only the average grades from the array of objects.

const students = [
  { name: 'Freddy', grade: 10, date: '20/07/2022' },
  { name: 'Jose', grade: 8, date:'20/07/2022' },
  { name: 'Freddy', grade: 8, date: '25/07/2022' },
  { name: 'Daniel', grade: 5, date: '21/07/2022' },
  { name: 'Jose', grade: 5 , date: '22/07/22'}
]

const grouped = students.reduce(
  (output, student) => {
    const name = student.name
    if (output[name]) {
      output[name].gradeTotal += student.grade;
      output[name].count += 1;
    }
    else {
      output[name] = {
        gradeTotal: student.grade,
        count: 1
      }
    }
   return output
  }, {})

console.log('Grouped by student: ', grouped)

const studentAverages = Object.keys(grouped).map(name => (
   {
    name,
    average: grouped[name].gradeTotal / grouped[name].count 
   }
  )
)

console.log('Student averages: ', studentAverages)

const justAverages = studentAverages.map(student => student.average)

console.log('Just averages:', justAverages)

Answer 2

In order to achieve this:

I opted to utilize the `reduce` method to construct a dictionary containing the sum of grades and grade count for each student.
- Choosing a dictionary was strategic as it facilitates easy navigation while `reduce` processes through the array.
Subsequently, I employed `Object.keys()` to extract an array of keys from the dictionary and then used `map` to convert this array into objects representing each student's average grade.
- This approach was selected based on the notion that the resulting output could prove beneficial. While it may have been more straightforward to iterate over the dictionary directly and transform it into a collection of average values, I found this method preferable.
We proceeded to use `map` to isolate and retrieve only the average grades from the array of objects.

const students = [
  { name: 'Freddy', grade: 10, date: '20/07/2022' },
  { name: 'Jose', grade: 8, date:'20/07/2022' },
  { name: 'Freddy', grade: 8, date: '25/07/2022' },
  { name: 'Daniel', grade: 5, date: '21/07/2022' },
  { name: 'Jose', grade: 5 , date: '22/07/22'}
]

const grouped = students.reduce(
  (output, student) => {
    const name = student.name
    if (output[name]) {
      output[name].gradeTotal += student.grade;
      output[name].count += 1;
    }
    else {
      output[name] = {
        gradeTotal: student.grade,
        count: 1
      }
    }
   return output
  }, {})

console.log('Grouped by student: ', grouped)

const studentAverages = Object.keys(grouped).map(name => (
   {
    name,
    average: grouped[name].gradeTotal / grouped[name].count 
   }
  )
)

console.log('Student averages: ', studentAverages)

const justAverages = studentAverages.map(student => student.average)

console.log('Just averages:', justAverages)

Answer 3

Answer №2

It seems that you are looking for a solution to your problem.

To tackle this issue, I created several variables such as sum, counter which help in counting the occurrence of each name, average and avgArr to store the averages.
Next, I implemented nested loops where the outer loop extracts each object name and stores it in the name variable. The inner loop then searches through the array, calculates the average grade for each person with that name, and appends it to the avgArr array.
In order to prevent duplicates, a checked property was added to each object. If an object is marked as true, it is skipped. If the property is missing, the object is processed, marked as true, and included in the calculations. This property can be removed if desired later on.

let arr =[
    { name: 'Freddy', grade: 10, date: '20/07/2022' },
    { name: 'Jose', grade: 8, date:'20/07/2022' },
    { name: 'Freddy', grade: 8, date: '25/07/2022' },
    { name: 'Daniel', grade: 5, date: '21/07/2022' },
    { name: 'Jose', grade: 5 , date: '22/07/22' }];
    let sum = 0;
    let counter = 0;
    let avg;
    const avgArr = [];
    for (const i of arr){
      let name = i.name;
      if (i.checked === true) {
        continue;
      }
      for (const j of arr){
        if (name === j.name) {
          j.checked = true;
          sum += j.grade;
          counter +=1;
        }
      }
      avg = sum / counter;                                                        
      avgArr.push(avg);
      sum = counter = 0;    
    }
     console.log(avgArr); // [9, 6.5, 5]

Answer 4

It seems that you are looking for a solution to your problem.

To tackle this issue, I created several variables such as sum, counter which help in counting the occurrence of each name, average and avgArr to store the averages.
Next, I implemented nested loops where the outer loop extracts each object name and stores it in the name variable. The inner loop then searches through the array, calculates the average grade for each person with that name, and appends it to the avgArr array.
In order to prevent duplicates, a checked property was added to each object. If an object is marked as true, it is skipped. If the property is missing, the object is processed, marked as true, and included in the calculations. This property can be removed if desired later on.

let arr =[
    { name: 'Freddy', grade: 10, date: '20/07/2022' },
    { name: 'Jose', grade: 8, date:'20/07/2022' },
    { name: 'Freddy', grade: 8, date: '25/07/2022' },
    { name: 'Daniel', grade: 5, date: '21/07/2022' },
    { name: 'Jose', grade: 5 , date: '22/07/22' }];
    let sum = 0;
    let counter = 0;
    let avg;
    const avgArr = [];
    for (const i of arr){
      let name = i.name;
      if (i.checked === true) {
        continue;
      }
      for (const j of arr){
        if (name === j.name) {
          j.checked = true;
          sum += j.grade;
          counter +=1;
        }
      }
      avg = sum / counter;                                                        
      avgArr.push(avg);
      sum = counter = 0;    
    }
     console.log(avgArr); // [9, 6.5, 5]

What is the best way to calculate the average grade for each student in an array that contains objects with exam submission data?

Answer №1

Answer №2

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