JavaScript Set Logic

Understanding Set operations and logic

🧠 What is Set Logic?

Set logic involves operations like union, intersection, and difference between sets. These operations help you compare and combine sets in useful ways. 


// Basic set logic example
const setA = new Set([1, 2, 3]);
const setB = new Set([3, 4, 5]);
console.log("Set A:", setA);
console.log("Set B:", setB);

Set Operations

🔗

Union

Combine all elements from both sets

🎯

Intersection

Find common elements in both sets

âž–

Difference

Elements in one set but not the other

🔄

Symmetric Difference

Elements in either set but not both

🔹 Union Operation

Union combines all unique elements from both sets: 

const setA = new Set([1, 2, 3]);
const setB = new Set([3, 4, 5]);

// Union: all elements from both sets
const union = new Set([...setA, ...setB]);
console.log("Union:", union);

Output:

Union: Set(5) {1, 2, 3, 4, 5}

🔹 Intersection Operation

Intersection finds elements that exist in both sets: 

const setA = new Set([1, 2, 3, 4]);
const setB = new Set([3, 4, 5, 6]);

// Intersection: common elements
const intersection = new Set([...setA].filter(x => setB.has(x)));
console.log("Intersection:", intersection);

Output:

Intersection: Set(2) {3, 4}

🔹 Difference Operation

Difference finds elements in the first set but not in the second: 

const setA = new Set([1, 2, 3, 4]);
const setB = new Set([3, 4, 5, 6]);

// Difference: elements in A but not in B
const difference = new Set([...setA].filter(x => !setB.has(x)));
console.log("Difference (A - B):", difference);

Output:

Difference (A - B): Set(2) {1, 2}

🔹 Symmetric Difference

Symmetric difference finds elements in either set but not in both: 

const setA = new Set([1, 2, 3, 4]);
const setB = new Set([3, 4, 5, 6]);

// Symmetric difference: elements in A or B but not both
const symDiff = new Set([
    ...[...setA].filter(x => !setB.has(x)),
    ...[...setB].filter(x => !setA.has(x))
]);
console.log("Symmetric Difference:", symDiff);

Output:

Symmetric Difference: Set(4) {1, 2, 5, 6}

🔹 Subset and Superset

Check if one set is contained within another:

Set Relationships:

  • Subset: All elements of A are in B
  • Superset: B contains all elements of A
  • Equal: Both sets have the same elements 
const setA = new Set([1, 2]);
const setB = new Set([1, 2, 3, 4]);

// Check if A is subset of B
const isSubset = [...setA].every(x => setB.has(x));
console.log("A is subset of B:", isSubset);

// Check if sets are equal
const areEqual = setA.size === setB.size && [...setA].every(x => setB.has(x));
console.log("Sets are equal:", areEqual);

Output:

A is subset of B: true
Sets are equal: false

🔹 Practical Set Logic Functions

Create reusable functions for set operations: 

// Utility functions for set operations
function union(setA, setB) {
    return new Set([...setA, ...setB]);
}

function intersection(setA, setB) {
    return new Set([...setA].filter(x => setB.has(x)));
}

function difference(setA, setB) {
    return new Set([...setA].filter(x => !setB.has(x)));
}

// Example usage
const fruits = new Set(['apple', 'banana', 'orange']);
const colors = new Set(['red', 'orange', 'yellow']);

console.log("Union:", union(fruits, colors));
console.log("Intersection:", intersection(fruits, colors));

Output:

Union: Set(5) {'apple', 'banana', 'orange', 'red', 'yellow'}
Intersection: Set(1) {'orange'}

🧠 Test Your Knowledge

What does the intersection of two sets contain?