Removing duplicate objects from array in JavaScript

Removing duplicate objects from arrays is a common requirement in JavaScript applications. Let's explore different approaches to eliminate duplicate objects while preserving the original data structure.

The Problem

Consider an array containing duplicate objects:

const arr = [
    {"title": "Assistant"},
    {"month": "July"},
    {"event": "Holiday"},
    {"title": "Assistant"}
];

console.log("Original array:", arr);

Original array: [
  { title: 'Assistant' },
  { month: 'July' },
  { event: 'Holiday' },
  { title: 'Assistant' }
]

Using JSON.stringify() with Filter

The most straightforward approach uses JSON.stringify() to convert objects to strings for comparison:

const arr = [
    {"title": "Assistant"},
    {"month": "July"},
    {"event": "Holiday"},
    {"title": "Assistant"}
];

const removeDuplicates = (array) => {
    const seen = new Set();
    return array.filter(obj => {
        const str = JSON.stringify(obj);
        if (seen.has(str)) {
            return false;
        }
        seen.add(str);
        return true;
    });
};

const uniqueArray = removeDuplicates(arr);
console.log("Unique objects:", uniqueArray);

Unique objects: [
  { title: 'Assistant' },
  { month: 'July' },
  { event: 'Holiday' }
]

In-Place Removal with Splice

For modifying the original array directly:

const arr = [
    {"title": "Assistant"},
    {"month": "July"},
    {"event": "Holiday"},
    {"title": "Assistant"}
];

const removeDuplicateInPlace = (array) => {
    const map = {};
    for(let i = 0; i 

Modified original array: [
  { title: 'Assistant' },
  { month: 'July' },
  { event: 'Holiday' }
]


Using Map for Better Performance

For larger datasets, using Map provides better performance than plain objects:

const arr = [
    {"title": "Assistant"},
    {"month": "July"},
    {"event": "Holiday"},
    {"title": "Assistant"},
    {"month": "July"}
];

const removeDuplicatesWithMap = (array) => {
    const seen = new Map();
    return array.filter(obj => {
        const key = JSON.stringify(obj);
        if (seen.has(key)) {
            return false;
        }
        seen.set(key, true);
        return true;
    });
};

const result = removeDuplicatesWithMap(arr);
console.log("Result with Map:", result);


Result with Map: [
  { title: 'Assistant' },
  { month: 'July' },
  { event: 'Holiday' }
]


Comparison of Methods

Key Points

• JSON.stringify() converts objects to strings for comparison
• Filter methods create new arrays without modifying the original
• In-place methods modify the original array directly
• Use Set or Map for better performance with large datasets

Conclusion

The filter approach with Set or Map is generally recommended as it's clean, functional, and performant. Use in-place methods only when memory conservation is critical.