JavaScript

JavaScript Set objects come with built-in methods that help you manage unique collections of values.

A Set ensures no duplicates, and you can perform various operations like adding, removing, and checking values.

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✅ List of Common Set Methods

Method	Description
add(value)	Adds a new value
delete(value)	Removes a specific value
has(value)	Checks if a value exists
clear()	Removes all values from the Set
values()	Returns an iterator of Set values
forEach(callback)	Loops through each value in the Set
size	Returns the number of values (property)

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🔹 add(value)

Adds a new unique value to the Set.

const items = new Set();
items.add("pen");
items.add("book");
items.add("pen"); // duplicate - ignored

console.log(items); // Set(2) { "pen", "book" }

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🔹 delete(value)

Removes a value from the Set.

items.delete("pen");

console.log(items); // Set(1) { "book" }

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🔹 has(value)

Checks if a value exists in the Set.

console.log(items.has("book"));  // true
console.log(items.has("pen"));   // false

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🔹 clear()

Deletes all elements in the Set.

items.clear();

console.log(items); // Set(0) {}

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🔹 values() or keys()

Returns an iterator of the Set’s values.

const letters = new Set(["a", "b", "c"]);

for (let letter of letters.values()) {
  console.log(letter);
}

Note: keys() is an alias for values() in Set (for consistency with Map).

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🔹 forEach(callback)

Loops through each value in the Set.

letters.forEach(value => {
  console.log(value);
});

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🔹 .size Property

Gives the total number of values in the Set.

console.log(letters.size); // 3

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🧾 Quick Example: All Methods in One

const numbers = new Set();

numbers.add(1);
numbers.add(2);
numbers.add(3);

console.log(numbers.has(2));   // true
numbers.delete(3);
console.log(numbers.size);     // 2

numbers.forEach(num => console.log(num)); // 1 2

numbers.clear();
console.log(numbers.size);     // 0

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✅ Summary Table

Method / Property	Purpose
add()	Add a value
delete()	Delete a specific value
has()	Check if value exists
clear()	Remove all values
values()	Get iterator of values
forEach()	Loop through values
size	Get number of values (read-only)

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