Logical Operators with in JavaScript

Logical operators are used to make decisions based on multiple conditions. In JavaScript, there are three types of logical operators:

  1. Logical AND (&&)
  2. Logical OR (||)
  3. Logical NOT (!)

Let's explore each of these operators with examples.

1. Logical AND (&&)

The logical AND operator returns true if both operands are true. Otherwise, it returns false.

Syntax:

operand1 && operand2
Example 1: Basic Usage
// Logical AND (&&)
// Returns TRUE if both operands are TRUE
console.log(true && true);  // Output: true
console.log(false && true); // Output: false

If either operand is false, the result is false.

Example 2: Real-world Use Case

Let's imagine we want to build an application for approving loans. The applicant must have a high income and a good credit score to be eligible for a loan.

let highIncome = true;
let goodCreditScore = true;
let eligibleForLoan = highIncome && goodCreditScore;

console.log(eligibleForLoan); // Output: true

If either highIncome or goodCreditScore is false, eligibleForLoan will be false.

2. Logical OR (||)

The logical OR operator returns true if at least one of the operands is true. If both operands are false, it returns false.

Syntax:

operand1 || operand2
Example 1: Basic Usage
// Logical OR (||)
// Returns TRUE if one of the operands is TRUE
console.log(true || false);  // Output: true
console.log(false || false); // Output: false

As long as one operand is true, the result is true.

Example 2: Real-world Use Case

Continuing with our loan application example, let's say an applicant can be eligible for a loan if they have either a high income or a good credit score.

let highIncome = false;
let goodCreditScore = true;
let eligibleForLoan = highIncome || goodCreditScore;

console.log(eligibleForLoan); // Output: true

If both highIncome and goodCreditScore are false, eligibleForLoan will be false.

3. Logical NOT (!)

The logical NOT operator inverts the value of its operand. If the operand is true, it returns false, and if the operand is false, it returns true.

Syntax:

!operand
Example: Real-world Use Case

Let's consider a scenario where we want to mark an application as refused if the applicant is not eligible for a loan.

let highIncome = false;
let goodCreditScore = false;
let eligibleForLoan = highIncome || goodCreditScore;
console.log('Eligible:', eligibleForLoan); // Output: false

// Logical NOT (!)
let applicationRefused = !eligibleForLoan;
console.log('Application Refused:', applicationRefused); // Output: true

Examples and Explanation

Logical AND (&&)

The logical AND operator returns true if both conditions are true.

let highIncome = true;
let goodCreditScore = true;
let eligibleForLoan = highIncome && goodCreditScore;
console.log(eligibleForLoan); // true

highIncome = false;
console.log(highIncome && goodCreditScore); // false

Logical OR (||)

The logical OR operator returns true if at least one condition is true.

let highIncome = false;
let goodCreditScore = true;
let eligibleForLoan = highIncome || goodCreditScore;
console.log(eligibleForLoan); // true

highIncome = false;
goodCreditScore = false;
console.log(highIncome || goodCreditScore); // false

Logical NOT (!)

The logical NOT operator inverts the boolean value.

let highIncome = false;
let goodCreditScore = false;
let eligibleForLoan = highIncome || goodCreditScore;
console.log('Eligible:', eligibleForLoan); // false

let applicationRefused = !eligibleForLoan;
console.log('Application Refused:', applicationRefused); // true

Summary

Logical operators in JavaScript are essential for making decisions based on multiple conditions:

  • Logical AND (&&): Returns true if both operands are true.

    • Syntax: operand1 && operand2
    • Example: console.log(true && true); // true

  • Logical OR (||): Returns true if at least one operand is true.

    • Syntax: operand1 || operand2
    • Example: console.log(true || false); // true

  • Logical NOT (!): Inverts the boolean value of its operand.

    • Syntax: !operand
    • Example: console.log(!true); // false

Understanding these operators will help you make complex logical decisions in your code, making your programs more flexible and robust.