JavaScript Sets
Understanding Sets - Collections of unique values
🎯 What are JavaScript Sets?
A Set is a collection of unique values. Unlike arrays, Sets automatically remove duplicate values and provide efficient methods for checking if a value exists.
// Creating a new Set
const mySet = new Set();
mySet.add(1);
mySet.add(2);
mySet.add(1); // Duplicate - won't be added
console.log(mySet); // Set {1, 2}
Output:
Set {1, 2}
Key Set Features
Unique Values
Automatically removes duplicates
const set = new Set([1, 1, 2, 3]);
// Result: Set {1, 2, 3}Fast Lookup
Quick checking if value exists
set.has(2); // true
set.has(5); // falseSize Property
Get number of unique values
set.size; // 3Iterable
Can be looped through
for (let value of set) {
console.log(value);
}🔹 Creating Sets
There are several ways to create a Set:
// Empty Set
const emptySet = new Set();
// Set from array
const arraySet = new Set([1, 2, 3, 4]);
// Set from string (each character)
const stringSet = new Set('hello');
console.log(stringSet); // Set {'h', 'e', 'l', 'o'}
// Set with mixed data types
const mixedSet = new Set([1, 'hello', true, null]);
console.log(mixedSet); // Set {1, 'hello', true, null}Output:
Set {'h', 'e', 'l', 'o'}
Set {1, 'hello', true, null}
Set {1, 'hello', true, null}
🔹 Basic Set Operations
Common operations you can perform with Sets:
const fruits = new Set();
// Adding values
fruits.add('apple');
fruits.add('banana');
fruits.add('orange');
fruits.add('apple'); // Won't be added (duplicate)
console.log(fruits.size); // 3
// Checking if value exists
console.log(fruits.has('apple')); // true
console.log(fruits.has('grape')); // false
// Removing values
fruits.delete('banana');
console.log(fruits.has('banana')); // false
// Clear all values
fruits.clear();
console.log(fruits.size); // 0Output:
3
true
false
false
0
true
false
false
0
🔹 Practical Set Examples
Real-world use cases for Sets:
🔸 Remove Duplicates from Array
const numbers = [1, 2, 2, 3, 4, 4, 5];
const uniqueNumbers = [...new Set(numbers)];
console.log(uniqueNumbers); // [1, 2, 3, 4, 5]Output:
[1, 2, 3, 4, 5]
🔸 Check Common Elements
const set1 = new Set([1, 2, 3]);
const set2 = new Set([2, 3, 4]);
// Find intersection (common elements)
const intersection = new Set([...set1].filter(x => set2.has(x)));
console.log(intersection); // Set {2, 3}Output:
Set {2, 3}