JavaScript Logical Operators

Logical operators in JavaScript are used to combine or negate Boolean values and expressions. They return true or false.

1️⃣ Logical Operators in JavaScript

Operator	Name	Example	Description
&&	Logical AND	a && b	Returns true if both a and b are true.
`		`	Logical OR
!	Logical NOT	!a	Returns true if a is false, and vice versa.

2️⃣ Logical AND (&&)

✅ Returns true only if both conditions are true.
🚫 If any condition is false, it returns false.

console.log(true && true);   // true
console.log(true && false);  // false
console.log(5 > 3 && 10 < 20); // true
console.log(5 > 3 && 10 > 20); // false

🔹 Use Case: Checking multiple conditions

let age = 25;
let hasID = true;

if (age >= 18 && hasID) {
    console.log("You can enter.");
} else {
    console.log("Access denied.");
}

3️⃣ Logical OR (||)

✅ Returns true if at least one condition is true.
🚫 Returns false only if both conditions are false.

console.log(true || false);  // true
console.log(false || false); // false
console.log(5 > 10 || 20 > 15); // true
console.log(5 > 10 || 20 < 15); // false

🔹 Use Case: Providing default values

let username = "";
let displayName = username || "Guest";  // If username is empty, use "Guest"
console.log(displayName); // "Guest"

4️⃣ Logical NOT (!)

✅ Negates a Boolean value (true → false, false → true).

console.log(!true);  // false
console.log(!false); // true
console.log(!(5 > 3)); // false (since 5 > 3 is true)

🔹 Use Case: Checking if a variable is falsy

let isLoggedIn = false;
if (!isLoggedIn) {
    console.log("Please log in.");
}

5️⃣ Short-Circuiting in Logical Operators

Logical AND (&&) Short-Circuiting

If the first operand is false, JavaScript stops evaluating and returns that value.

console.log(false && "Hello"); // false (does not evaluate "Hello")
console.log(true && "Hello");  // "Hello" (evaluates second operand)

Logical OR (||) Short-Circuiting

If the first operand is true, JavaScript stops evaluating and returns that value.

console.log(true || "Hello");  // true (stops at first operand)
console.log(false || "Hello"); // "Hello" (evaluates second operand)

🔹 Use Case: Setting default values

let user = null;
let userName = user || "Anonymous"; // If user is null, use "Anonymous"
console.log(userName); // "Anonymous"

6️⃣ Combining Logical Operators

You can combine &&, ||, and ! in complex conditions.

let age = 20;
let hasLicense = true;

if (age >= 18 && hasLicense) {
    console.log("You can drive.");
} else {
    console.log("You cannot drive.");
}

🎯 Summary

✅ && (AND) → Both must be true
✅ || (OR) → At least one must be true
✅ ! (NOT) → Reverses the Boolean value
✅ Short-circuiting improves performance
✅ Use OR (||) for default values

🚀 Now you can handle logical conditions in JavaScript like a pro! Let me know if you need more details. 😊