javascript reduce to the specified array

Question

javascript reduce to the specified array

Having an array called List that consists of objects with id, name, and grade properties. I'm working on designing a dropdown menu in React where the name is displayed on the left and the corresponding grades are displayed in the dropdown on the right. However, I'm facing an issue where only grades belonging to a specific name should be shown in the dropdown.

const List = [
{id:1, name:"jack", grade:'98'},
{id:2, name:"jack", grade:'96'},
{id:3, name:"jack", grade:'80'},
{id:4, name:"jack", grade:'76'},
{id:5, name:"jack", grade:'78'},
{id:6, name:"marry", grade:'90'},
{id:7, name:"marry", grade:'91'},
{id:8, name:"marry", grade:'96'},
{id:9, name:"marry", grade:'95'},
{id:10, name:"marry", grade:'82'},
{id:11, name:"paul", grade:'87'},
{id:12, name:"paul", grade:'98'},
{id:13, name:"paul", grade:'95'},
{id:14, name:"paul", grade:'93'},
{id:15, name:"paul", grade:'75'},
]

To tackle this problem, I need to create new arrays containing the grades for each individual name. For example, when the name is jack, the grade array should be [98, 96, 80, 76, 78]. Similarly, when the name is marry, the grade array should be [90, 91, 96, 95, 82]. I've attempted using the .map() method but need guidance on how to properly iterate through each name to achieve this behavior.

javascript arrays

Answer 1

Answer №1

To retrieve a list of objects and their corresponding grades, utilize the filter method to extract the objects and then use map to isolate the grades as shown below:

const List = [
{id:1, name:"jack", grade:'98'},
{id:2, name:"jack", grade:'96'},
{id:3, name:"jack", grade:'80'},
{id:4, name:"jack", grade:'76'},
{id:5, name:"jack", grade:'78'},
{id:6, name:"marry", grade:'90'},
{id:7, name:"marry", grade:'91'},
{id:8, name:"marry", grade:'96'},
{id:9, name:"marry", grade:'95'},
{id:10, name:"marry", grade:'82'},
{id:11, name:"paul", grade:'87'},
{id:12, name:"paul", grade:'98'},
{id:13, name:"paul", grade:'95'},
{id:14, name:"paul", grade:'93'},
{id:15, name:"paul", grade:'75'},
];

const getGrade = name => List.filter(val => val.name === name).map(info => info.grade);

console.log('jack',getGrade('jack'));
console.log('paul',getGrade('paul'));

Answer 2

To retrieve a list of objects and their corresponding grades, utilize the filter method to extract the objects and then use map to isolate the grades as shown below:

const List = [
{id:1, name:"jack", grade:'98'},
{id:2, name:"jack", grade:'96'},
{id:3, name:"jack", grade:'80'},
{id:4, name:"jack", grade:'76'},
{id:5, name:"jack", grade:'78'},
{id:6, name:"marry", grade:'90'},
{id:7, name:"marry", grade:'91'},
{id:8, name:"marry", grade:'96'},
{id:9, name:"marry", grade:'95'},
{id:10, name:"marry", grade:'82'},
{id:11, name:"paul", grade:'87'},
{id:12, name:"paul", grade:'98'},
{id:13, name:"paul", grade:'95'},
{id:14, name:"paul", grade:'93'},
{id:15, name:"paul", grade:'75'},
];

const getGrade = name => List.filter(val => val.name === name).map(info => info.grade);

console.log('jack',getGrade('jack'));
console.log('paul',getGrade('paul'));

Answer 3

Answer №2

const StudentList = [
{id:1, name:"Alice", grade:'95'},
{id:2, name:"Alice", grade:'98'},
{id:3, name:"Alice", grade:'85'},
{id:4, name:"Alice", grade:'90'},
{id:5, name:"Alice", grade:'88'},
{id:6, name:"Bob", grade:'92'},
{id:7, name:"Bob", grade:'93'},
{id:8, name:"Bob", grade:'96'},
{id:9, name:"Bob", grade:'94'},
{id:10, name:"Bob", grade:'87'},
{id:11, name:"Charlie", grade:'89'},
{id:12, name:"Charlie", grade:'96'},
{id:13, name:"Charlie", grade:'93'},
{id:14, name:"Charlie", grade:'91'},
{id:15, name:"Charlie", grade:'83'},
]
const gradesByStudentName = {};
StudentList.map(student => {
    if(!gradesByStudentName[student.name]) {
        gradesByStudentName[student.name] = [];
    }
    gradesByStudentName[student.name].push(student.grade);
})
console.log(gradesByStudentName);

Answer 4

const StudentList = [
{id:1, name:"Alice", grade:'95'},
{id:2, name:"Alice", grade:'98'},
{id:3, name:"Alice", grade:'85'},
{id:4, name:"Alice", grade:'90'},
{id:5, name:"Alice", grade:'88'},
{id:6, name:"Bob", grade:'92'},
{id:7, name:"Bob", grade:'93'},
{id:8, name:"Bob", grade:'96'},
{id:9, name:"Bob", grade:'94'},
{id:10, name:"Bob", grade:'87'},
{id:11, name:"Charlie", grade:'89'},
{id:12, name:"Charlie", grade:'96'},
{id:13, name:"Charlie", grade:'93'},
{id:14, name:"Charlie", grade:'91'},
{id:15, name:"Charlie", grade:'83'},
]
const gradesByStudentName = {};
StudentList.map(student => {
    if(!gradesByStudentName[student.name]) {
        gradesByStudentName[student.name] = [];
    }
    gradesByStudentName[student.name].push(student.grade);
})
console.log(gradesByStudentName);

Answer 5

Answer №3

It seems like you're looking to condense the array, not just extract grades for each individual. Here's one way to achieve that:

const StudentData = [
{id:1, name:"jack", grade:'98'},
{id:2, name:"jack", grade:'96'},
{id:3, name:"jack", grade:'80'},
{id:4, name:"jack", grade:'76'},
{id:5, name:"jack", grade:'78'},
{id:6, name:"marry", grade:'90'},
{id:7, name:"marry", grade:'91'},
{id:8, name:"marry", grade:'96'},
{id:9, name:"marry", grade:'95'},
{id:10, name:"marry", grade:'82'},
{id:11, name:"paul", grade:'87'},
{id:12, name:"paul", grade:'98'},
{id:13, name:"paul", grade:'95'},
{id:14, name:"paul", grade:'93'},
{id:15, name:"paul", grade:'75'},
];
const condensedList = StudentData.reduce((accumulated, current) => {
  const found = accumulated.find(item => item.name === current.name);
  if (found) found.grade.push(current.grade);
  else {
    accumulated.push({
      name: current.name,
      grade: [current.grade],
    });
  }
  return accumulated;
}, []);


console.log(condensedList);
// [ { name: 'jack', grade: [ '98', '96', '80', '76', '78' ] },
// { name: 'marry', grade: [ '90', '91', '96', '95', '82' ] },
// { name: 'paul', grade: [ '87', '98', '95', '93', '75' ] } ]

Answer 6

It seems like you're looking to condense the array, not just extract grades for each individual. Here's one way to achieve that:

const StudentData = [
{id:1, name:"jack", grade:'98'},
{id:2, name:"jack", grade:'96'},
{id:3, name:"jack", grade:'80'},
{id:4, name:"jack", grade:'76'},
{id:5, name:"jack", grade:'78'},
{id:6, name:"marry", grade:'90'},
{id:7, name:"marry", grade:'91'},
{id:8, name:"marry", grade:'96'},
{id:9, name:"marry", grade:'95'},
{id:10, name:"marry", grade:'82'},
{id:11, name:"paul", grade:'87'},
{id:12, name:"paul", grade:'98'},
{id:13, name:"paul", grade:'95'},
{id:14, name:"paul", grade:'93'},
{id:15, name:"paul", grade:'75'},
];
const condensedList = StudentData.reduce((accumulated, current) => {
  const found = accumulated.find(item => item.name === current.name);
  if (found) found.grade.push(current.grade);
  else {
    accumulated.push({
      name: current.name,
      grade: [current.grade],
    });
  }
  return accumulated;
}, []);


console.log(condensedList);
// [ { name: 'jack', grade: [ '98', '96', '80', '76', '78' ] },
// { name: 'marry', grade: [ '90', '91', '96', '95', '82' ] },
// { name: 'paul', grade: [ '87', '98', '95', '93', '75' ] } ]

Answer 7

Answer №4

Construct an object where the keys represent names and the values are a collection of grades by utilizing the forEach method for efficient data aggregation.

const StudentList = [
{id:1, name:"jack", grade:'98'},
{id:2, name:"jack", grade:'96'},
{id:3, name:"jack", grade:'80'},
{id:4, name:"jack", grade:'76'},
{id:5, name:"jack", grade:'78'},
{id:6, name:"marry", grade:'90'},
{id:7, name:"marry", grade:'91'},
{id:8, name:"marry", grade:'96'},
{id:9, name:"marry", grade:'95'},
{id:10, name:"marry", grade:'82'},
{id:11, name:"paul", grade:'87'},
{id:12, name:"paul", grade:'98'},
{id:13, name:"paul", grade:'95'},
{id:14, name:"paul", grade:'93'},
{id:15, name:"paul", grade:'75'},
]

const studentGrades = {};
StudentList.forEach(
  ({ name, grade }) => (studentGrades[name] = (studentGrades[name] ?? []).concat([grade]))
);

console.log(studentGrades["jack"]);
console.log(studentGrades["paul"]);

Answer 8

Construct an object where the keys represent names and the values are a collection of grades by utilizing the forEach method for efficient data aggregation.

const StudentList = [
{id:1, name:"jack", grade:'98'},
{id:2, name:"jack", grade:'96'},
{id:3, name:"jack", grade:'80'},
{id:4, name:"jack", grade:'76'},
{id:5, name:"jack", grade:'78'},
{id:6, name:"marry", grade:'90'},
{id:7, name:"marry", grade:'91'},
{id:8, name:"marry", grade:'96'},
{id:9, name:"marry", grade:'95'},
{id:10, name:"marry", grade:'82'},
{id:11, name:"paul", grade:'87'},
{id:12, name:"paul", grade:'98'},
{id:13, name:"paul", grade:'95'},
{id:14, name:"paul", grade:'93'},
{id:15, name:"paul", grade:'75'},
]

const studentGrades = {};
StudentList.forEach(
  ({ name, grade }) => (studentGrades[name] = (studentGrades[name] ?? []).concat([grade]))
);

console.log(studentGrades["jack"]);
console.log(studentGrades["paul"]);

Answer 9

Answer №5

To start, you can create an array to store the names of all students. Then, by using the map function, generate an array of objects that will provide the desired result.

let studentList = [
{id:1, name:"jack", grade:'98'},
{id:2, name:"jack", grade:'96'},
{id:3, name:"jack", grade:'80'},
{id:4, name:"jack", grade:'76'},
{id:5, name:"jack", grade:'78'},
{id:6, name:"marry", grade:'90'},
{id:7, name:"marry", grade:'91'},
{id:8, name:"marry", grade:'96'},
{id:9, name:"marry", grade:'95'},
{id:10, name:"marry", grade:'82'},
{id:11, name:"paul", grade:'87'},
{id:12, name:"paul", grade:'98'},
{id:13, name:"paul", grade:'95'},
{id:14, name:"paul", grade:'93'},
{id:15, name:"paul", grade:'75'},
]

let students = [];
let grades = [];
for(let record of studentList) {
    if(!students.includes(record.name)) students.push(record.name);
}
console.log(students);
students.map(student => {
    let gradeList = [], studentObj={};
    studentList.map(data => {        
        if(data.name === student) gradeList.push(data.grade);
    })
    studentObj.name = student;
    studentObj.grades = gradeList;
    grades.push(studentObj);
})
console.log(grades);

Answer 10

To start, you can create an array to store the names of all students. Then, by using the map function, generate an array of objects that will provide the desired result.

let studentList = [
{id:1, name:"jack", grade:'98'},
{id:2, name:"jack", grade:'96'},
{id:3, name:"jack", grade:'80'},
{id:4, name:"jack", grade:'76'},
{id:5, name:"jack", grade:'78'},
{id:6, name:"marry", grade:'90'},
{id:7, name:"marry", grade:'91'},
{id:8, name:"marry", grade:'96'},
{id:9, name:"marry", grade:'95'},
{id:10, name:"marry", grade:'82'},
{id:11, name:"paul", grade:'87'},
{id:12, name:"paul", grade:'98'},
{id:13, name:"paul", grade:'95'},
{id:14, name:"paul", grade:'93'},
{id:15, name:"paul", grade:'75'},
]

let students = [];
let grades = [];
for(let record of studentList) {
    if(!students.includes(record.name)) students.push(record.name);
}
console.log(students);
students.map(student => {
    let gradeList = [], studentObj={};
    studentList.map(data => {        
        if(data.name === student) gradeList.push(data.grade);
    })
    studentObj.name = student;
    studentObj.grades = gradeList;
    grades.push(studentObj);
})
console.log(grades);

javascript reduce to the specified array

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

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