What is a Set in JS?

A Set is a collection of unique values. Unlike arrays, sets cannot have duplicate elements.

Basic Operations with Set

Creating a Set

You can create a new Set using the new Set() constructor. For example:

const uniqueNumbers = new Set([1, 2, 3, 3, 4]);
console.log(uniqueNumbers); // Output: Set(4) {1, 2, 3, 4}

Funny-Serious Examples

Example 1: The Duplicate Party Crashers
Imagine you’re having a party, and you only want unique guests. But some guests try to sneak in twice!

const partyGuests = new Set();

partyGuests.add('Alice');
partyGuests.add('Bob');
partyGuests.add('Alice'); // Alice tries to sneak in again!

console.log(partyGuests); // Output: Set(2) {"Alice", "Bob"}

Here, Alice tried to sneak in twice, but the Set only lets her in once.

Example 2: The Magic Hat Trick
You have a magic hat that only allows unique items to be stored. If you try to put the same item twice, it just won’t have it!

const magicHat = new Set();

magicHat.add('Rabbit');
magicHat.add('Dove');
magicHat.add('Rabbit'); // Another Rabbit tries to jump in!

console.log(magicHat); // Output: Set(2) {"Rabbit", "Dove"}

The magic hat only contains one rabbit and one dove, despite the second rabbit trying to jump in.

Example 3: The Library of Unique Books
You run a library where each book must be unique. If someone tries to donate a book you already have, you politely decline.

const library = new Set(['1984', 'Brave New World', '1984']); // 1984 is already in the library!

console.log(library); // Output: Set(2) {"1984", "Brave New World"}

Your library maintains its uniqueness by only keeping one copy of each book.

Useful Methods

Checking for a Member

Want to know if a particular guest is already at the party?

console.log(partyGuests.has('Alice')); // true
console.log(partyGuests.has('Charlie')); // false

Removing a Member

Someone decides to leave the party early? No problem!

partyGuests.delete('Bob');
console.log(partyGuests); // Output: Set(1) {"Alice"}

Clearing the Set

Party's over! Time to clear everyone out.

partyGuests.clear();
console.log(partyGuests); // Output: Set(0) {}

Iterating Over a Set

Just like arrays, you can iterate over sets.

const animals = new Set(['Cat', 'Dog', 'Bird']);

for (const animal of animals) {
  console.log(animal); 
  // Output:
  // Cat
  // Dog
  // Bird
}

Converting Between Sets and Arrays

You can convert a set to an array and vice versa.

const numberSet = new Set([1, 2, 3]);
const numberArray = [...numberSet]; // [1, 2, 3]

const arrayToSet = new Set(numberArray); // Set(3) {1, 2, 3}

Why Use a Set?

Sets are particularly useful when you need to store a collection of unique items, and you want to avoid duplicates without having to manually check for them.

Summary

• Unique Values: Sets store only unique values.
• Basic Operations: You can add, delete, and check for values in a set.
• Iterate: You can iterate over the values in a set.
• Conversion: Easily convert between sets and arrays.

By using sets, you ensure that your collections remain unique and efficient, whether it’s a guest list for a party, items in a magic hat, or books in a library!