JavaScript Numbers
Working with numeric data in JavaScript
🔢 What are JavaScript Numbers?
JavaScript has only one type of number - they can be integers or floating-point numbers. Unlike other languages, JavaScript doesn't distinguish between different number types.
// All of these are numbers in JavaScript
let integer = 42;
let decimal = 3.14159;
let negative = -17;
let scientific = 2.5e6; // 2,500,000
console.log(typeof integer); // Output: number
console.log(typeof decimal); // Output: number
Number Formats
Integers
Whole numbers without decimals
let age = 25;
let count = 100;Decimals
Numbers with decimal points
let price = 19.99;
let pi = 3.14159;Scientific Notation
Very large or small numbers
let big = 1.5e6; // 1,500,000
let small = 2.5e-4; // 0.00025Special Values
Infinity, -Infinity, and NaN
let inf = Infinity;
let notNum = NaN;🔹 Number Creation and Conversion
Different ways to create and convert numbers:
// Creating numbers
let num1 = 42; // Number literal
let num2 = new Number(42); // Number constructor (not recommended)
let num3 = Number("42"); // Convert string to number
let num4 = parseInt("42"); // Parse integer from string
let num5 = parseFloat("3.14"); // Parse float from string
console.log(num1); // Output: 42
console.log(num3); // Output: 42
console.log(num4); // Output: 42
console.log(num5); // Output: 3.14
// Converting to numbers
let str = "123";
let converted1 = Number(str); // 123
let converted2 = parseInt(str); // 123
let converted3 = +str; // 123 (unary plus operator)
console.log(converted1, converted2, converted3); // Output: 123 123 123Output:
42
42
42
3.14
123 123 123
🔹 Number Methods
Built-in methods for working with numbers:
let num = 123.456789;
// Convert to string
console.log(num.toString()); // Output: "123.456789"
// Fixed decimal places
console.log(num.toFixed(2)); // Output: "123.46"
console.log(num.toFixed(0)); // Output: "123"
// Precision (total digits)
console.log(num.toPrecision(5)); // Output: "123.46"
console.log(num.toPrecision(3)); // Output: "123"
// Exponential notation
console.log(num.toExponential(2)); // Output: "1.23e+2"
// Value of (for Number objects)
let numObj = new Number(42);
console.log(numObj.valueOf()); // Output: 42Output:
"123.456789"
"123.46"
"123"
"123.46"
"123"
"1.23e+2"
42
🔹 Number Properties and Constants
JavaScript provides useful number constants:
// Number properties
console.log(Number.MAX_VALUE); // Largest possible number
console.log(Number.MIN_VALUE); // Smallest positive number
console.log(Number.MAX_SAFE_INTEGER); // Largest safe integer
console.log(Number.MIN_SAFE_INTEGER); // Smallest safe integer
console.log(Number.POSITIVE_INFINITY); // Positive infinity
console.log(Number.NEGATIVE_INFINITY); // Negative infinity
console.log(Number.NaN); // Not a Number
// Checking number types
let testNum = 42;
console.log(Number.isInteger(testNum)); // Output: true
console.log(Number.isInteger(42.5)); // Output: false
console.log(Number.isNaN(NaN)); // Output: true
console.log(Number.isNaN(42)); // Output: false
console.log(Number.isFinite(42)); // Output: true
console.log(Number.isFinite(Infinity)); // Output: falseOutput:
1.7976931348623157e+308
5e-324
9007199254740991
-9007199254740991
Infinity
-Infinity
NaN
true
false
true
false
true
false
🔹 Math Object
JavaScript's Math object provides mathematical functions:
// Math constants
console.log(Math.PI); // Output: 3.141592653589793
console.log(Math.E); // Output: 2.718281828459045
// Rounding methods
console.log(Math.round(4.7)); // Output: 5 (round to nearest)
console.log(Math.ceil(4.1)); // Output: 5 (round up)
console.log(Math.floor(4.9)); // Output: 4 (round down)
console.log(Math.trunc(4.9)); // Output: 4 (remove decimal)
// Min and Max
console.log(Math.min(1, 3, 2)); // Output: 1
console.log(Math.max(1, 3, 2)); // Output: 3
// Power and square root
console.log(Math.pow(2, 3)); // Output: 8 (2^3)
console.log(Math.sqrt(16)); // Output: 4
console.log(Math.abs(-5)); // Output: 5 (absolute value)
// Random numbers
console.log(Math.random()); // Output: random number 0-1
console.log(Math.floor(Math.random() * 10)); // Random 0-9Output:
3.141592653589793
2.718281828459045
5
5
4
4
1
3
8
4
5
0.7234567891234567 (example)
7 (example)
🔹 Number Precision and Floating Point
Understanding JavaScript number precision:
// Floating point precision issues
console.log(0.1 + 0.2); // Output: 0.30000000000000004
console.log(0.1 + 0.2 === 0.3); // Output: false
// Solutions for precision
let sum = 0.1 + 0.2;
console.log(sum.toFixed(1)); // Output: "0.3"
console.log(Math.round(sum * 10) / 10); // Output: 0.3
// Safe integer range
console.log(Number.MAX_SAFE_INTEGER); // 9007199254740991
console.log(Number.MAX_SAFE_INTEGER + 1); // 9007199254740992
console.log(Number.MAX_SAFE_INTEGER + 2); // 9007199254740992 (same!)
// Checking if number is safe
console.log(Number.isSafeInteger(9007199254740991)); // true
console.log(Number.isSafeInteger(9007199254740992)); // falseOutput:
0.30000000000000004
false
"0.3"
0.3
9007199254740991
9007199254740992
9007199254740992
true
false
🔹 Practical Number Examples
Real-world number operations:
Common Number Tasks:
- Currency: Formatting prices and calculations
- Percentages: Calculating discounts and taxes
- Random Numbers: Games and simulations
- Validation: Checking if input is a valid number
// Currency formatting
let price = 19.99;
let tax = 0.08;
let total = price * (1 + tax);
console.log(`Total: $${total.toFixed(2)}`); // Output: Total: $21.59
// Percentage calculation
let score = 85;
let maxScore = 100;
let percentage = (score / maxScore) * 100;
console.log(`Score: ${percentage}%`); // Output: Score: 85%
// Random number in range
function randomBetween(min, max) {
return Math.floor(Math.random() * (max - min + 1)) + min;
}
console.log(randomBetween(1, 10)); // Random number 1-10
// Input validation
function isValidNumber(input) {
return !isNaN(input) && isFinite(input);
}
console.log(isValidNumber("42")); // Output: true
console.log(isValidNumber("abc")); // Output: false