Lesson 5: JavaScript Arithmetic Operations

Master JavaScript arithmetic operations with interactive examples and real-world applications.

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5.1 Arithmetic Operations in JavaScript

JavaScript provides a comprehensive set of arithmetic operators that allow you to perform mathematical operations. These operators work with numbers (both integers and floating-point values) and can be used for calculations in your programs.

Important: JavaScript follows standard mathematical operator precedence (PEMDAS/BODMAS rules) when evaluating expressions.

Basic Arithmetic Operators

JavaScript supports the following fundamental arithmetic operators:

Addition (+)

Adds two numbers together

let sum = 10 + 5; // 15

Subtraction (-)

Subtracts one number from another

let diff = 10 - 5; // 5

Multiplication (*)

Multiplies two numbers

let product = 10 * 5; // 50

Division (/)

Divides one number by another

let quotient = 10 / 5; // 2

Modulus (%)

Returns the division remainder

let remainder = 10 % 3; // 1

Exponentiation (**)

Raises a number to a power

let power = 2 ** 3; // 8

5.2 Interactive Arithmetic Demos

Try these interactive demos to see JavaScript arithmetic in action:

Basic Calculator

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Operator Precedence Demo

JavaScript follows specific rules for the order of operations. Try these examples to see how precedence works:

Example 1: 2 + 3 * 4

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Example 2: (2 + 3) * 4

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Example 3: 10 / 2 ** 2

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5.3 Advanced Operators

JavaScript also provides compound assignment operators and increment/decrement operators for more concise code:

Compound Assignment Operators

let x = 10;

// Addition assignment
x += 5; // x = x + 5 → 15

// Subtraction assignment
x -= 3; // x = x - 3 → 12

// Multiplication assignment
x *= 2; // x = x * 2 → 24

// Division assignment
x /= 4; // x = x / 4 → 6

// Modulus assignment
x %= 4; // x = x % 4 → 2

// Exponentiation assignment
x **= 3; // x = x ** 3 → 8

Increment and Decrement Operators

let count = 5;

// Postfix increment
count++; // Returns 5, then sets count to 6

// Prefix increment
++count; // Sets count to 7, then returns 7

// Postfix decrement
count--; // Returns 7, then sets count to 6

// Prefix decrement
--count; // Sets count to 5, then returns 5

Increment/Decrement Demo

See how increment and decrement operators work:

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5.4 Practical Applications

Arithmetic operations are fundamental to many real-world applications. Here are some practical examples:

Example 5.4(a): Calculating Area and Perimeter

// Calculate rectangle area and perimeter
function calculateRectangle() {
    const width = parseFloat(prompt("Enter rectangle width:"));
    const height = parseFloat(prompt("Enter rectangle height:"));
    
    const area = width * height;
    const perimeter = 2 * (width + height);
    
    return `Area: ${area}, Perimeter: ${perimeter}`;
}

// Calculate circle area and circumference
function calculateCircle() {
    const radius = parseFloat(prompt("Enter circle radius:"));
    const PI = Math.PI;
    
    const area = PI * radius ** 2;
    const circumference = 2 * PI * radius;
    
    return `Area: ${area.toFixed(2)}, Circumference: ${circumference.toFixed(2)}`;
}

Try it yourself:

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Example 5.4(b): Financial Calculations

// Calculate compound interest
function calculateInterest() {
    const principal = parseFloat(prompt("Principal amount:"));
    const rate = parseFloat(prompt("Annual interest rate (%):"));
    const years = parseInt(prompt("Number of years:"));
    const compounds = parseInt(prompt("Compounds per year:"));
    
    const r = rate / 100;
    const amount = principal * (1 + r/compounds) ** (compounds * years);
    const interest = amount - principal;
    
    return `Total amount: $${amount.toFixed(2)}, Interest earned: $${interest.toFixed(2)}`;
}

// Calculate loan payments
function calculateLoanPayment() {
    const loanAmount = parseFloat(prompt("Loan amount:"));
    const interestRate = parseFloat(prompt("Annual interest rate (%):"));
    const loanTerm = parseInt(prompt("Loan term (years):"));
    
    const r = interestRate / 100 / 12; // Monthly interest rate
    const n = loanTerm * 12; // Total months
    
    // Monthly payment formula
    const monthlyPayment = loanAmount * r * (1 + r) ** n / ((1 + r) ** n - 1);
    
    return `Monthly payment: $${monthlyPayment.toFixed(2)}`;
}

Try financial calculations:

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