Exploring the Differences Between Arrays of Objects and Arrays in JavaScript

Question

Exploring the Differences Between Arrays of Objects and Arrays in JavaScript

While working on a project for a client, I encountered an interesting problem. I have two arrays - one with objects and one with values. The task is to populate the array of objects with new objects for every item in the value array. To clarify, here is the code snippet and the expected output:

// Arrays: worksheet and data
var worksheet   = [{"student_name": "Test 1", "file": "some_file_name.txt"}, {"student_name": "Test 3", "file": "some_file_name.txt"}]
var data        = {"student_names": ["Test 1", "Test 2", "Test 3", "Test 4"]}

The goal is to iterate through data.student_names and add students that are not already in the worksheet.

// Expected Output:
var worksheet = [
    {"student_name": "Test 1", "file": "some_file_name.txt"},
    {"student_name": "Test 3", "file": "some_file_name.txt"},
    {"student_name": "Test 2", "file": ""}, // New student
    {"student_name": "Test 4", "file": ""}, // New student
]

javascript arrays json object

Answer 1

Answer №1

const studentData = [
  { 'name': 'Alex', 'file': 'document1.txt' },
  { 'name': 'John', 'file': 'document2.txt' }
]

const testData = { 'names': [ 'Alex', 'Lisa', 'John', 'Mike' ] }

const resultData = testData['names']
  .map(name => {
      let record = studentData.filter(item => item['name'] === name)
      let file = record.length === 0 ? '' : record[0].file
      return { 'student_name': name, 'file': file }
    }
)

console.log(resultData)

Answer 2

const studentData = [
  { 'name': 'Alex', 'file': 'document1.txt' },
  { 'name': 'John', 'file': 'document2.txt' }
]

const testData = { 'names': [ 'Alex', 'Lisa', 'John', 'Mike' ] }

const resultData = testData['names']
  .map(name => {
      let record = studentData.filter(item => item['name'] === name)
      let file = record.length === 0 ? '' : record[0].file
      return { 'student_name': name, 'file': file }
    }
)

console.log(resultData)

Answer 3

Answer №2

Approach

We will iterate over the list of student names stored in data.student_names and verify if each name exists within the worksheet. If a match is found, we will add the corresponding student object to the foundArr; otherwise, we will create an entry for the student name with an empty file in the notFoundArr. Finally, we will merge both arrays to obtain the desired output.

Implementation

const worksheet = [{"student_name": "Test 1", "file": "some_file_name.txt"}, {"student_name": "Test 3", "file": "some_file_name.txt"}];
const data = {"student_names": ["Test 1", "Test 2", "Test 3", "Test 4"]};
let foundArr = [];
let notFoundArr = [];
data.student_names.forEach(s => {
  let studentFound = worksheet.find(ws => ws.student_name === s);
  if (studentFound !== undefined){
    foundArr.push(studentFound);
  }
  else {
    notFoundArr.push({"student_name": s, "file":""});
  }
});
let result = foundArr.concat(notFoundArr);
console.log(result);

Answer 4

Approach

We will iterate over the list of student names stored in data.student_names and verify if each name exists within the worksheet. If a match is found, we will add the corresponding student object to the foundArr; otherwise, we will create an entry for the student name with an empty file in the notFoundArr. Finally, we will merge both arrays to obtain the desired output.

Implementation

const worksheet = [{"student_name": "Test 1", "file": "some_file_name.txt"}, {"student_name": "Test 3", "file": "some_file_name.txt"}];
const data = {"student_names": ["Test 1", "Test 2", "Test 3", "Test 4"]};
let foundArr = [];
let notFoundArr = [];
data.student_names.forEach(s => {
  let studentFound = worksheet.find(ws => ws.student_name === s);
  if (studentFound !== undefined){
    foundArr.push(studentFound);
  }
  else {
    notFoundArr.push({"student_name": s, "file":""});
  }
});
let result = foundArr.concat(notFoundArr);
console.log(result);

Exploring the Differences Between Arrays of Objects and Arrays in JavaScript

Answer №1

Answer №2

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