Overview of Numbers

In JavaScript, numbers are a fundamental data type used to represent numeric values. JavaScript has a single Number type for both integers and floating-point numbers.

Number Type

• JavaScript numbers can be written with or without decimals:

let integer = 42;       // Integer
let float = 3.14;       // Floating-point
let negative = -100;    // Negative number

Number Representation

• Integers: Whole numbers, e.g., 10, 5
• Floating-point: Numbers with decimals, e.g., 3.14, 0.001
• Scientific Notation: For very large or small numbers, e.g., 2e3 = 2000, 1e-3 = 0.001

Special Values:

• Infinity – Represents a value larger than any number (1 / 0)
• Infinity – Negative infinity (1 / 0)
• NaN – "Not a Number" (0 / 0 or parseInt("abc"))

Number Limits

• JavaScript uses 64-bit floating-point representation (IEEE 754)
• Maximum safe integer: Number.MAX_SAFE_INTEGER → 9007199254740991
• Minimum safe integer: Number.MIN_SAFE_INTEGER → 9007199254740991
• Beyond these, precision may be lost

Common Operations

• Arithmetic: +, , , /, % (modulus), * (exponentiation)

let sum = 10 + 5;      // 15
let power = 2 ** 3;    // 8

• Increment / Decrement: ++, -

let x = 5;
x++;                   // x = 6

• Type Coercion: JS automatically converts strings to numbers in some operations

let result = "5" * 2;  // 10

Built-in Methods

Number Methods:

• toFixed(n) – Formats number to n decimal places

let num = 3.14159;
console.log(num.toFixed(2)); // "3.14"

• toPrecision(n) – Formats number to n significant digits
• parseInt(string) – Converts string to integer
• parseFloat(string) – Converts string to floating-point
• isNaN(value) – Checks if value is NaN
• isFinite(value) – Checks if value is a finite number

Math Object Methods:

• Math.round(num) – Round to nearest integer
• Math.floor(num) – Round down
• Math.ceil(num) – Round up
• Math.random() – Random number between 0 (inclusive) and 1 (exclusive)

console.log(Math.floor(3.7)); // 3
console.log(Math.random());    // e.g., 0.723...

BigInt

• For integers larger than Number.MAX_SAFE_INTEGER, use BigInt

let bigNum = 123456789012345678901234567890n;
let anotherBigNum = BigInt("123456789012345678901234567890");

Common Pitfalls

• Floating-Point Precision:

console.log(0.1 + 0.2); // 0.30000000000000004

• Type Coercion:

console.log("5" + 3); // "53" (string concatenation)

Type Checking

• typeof – Check if a value is a number

console.log(typeof 42); // "number"
console.log(typeof NaN); // "number"

• Number.isInteger() – Check for integers

console.log(Number.isInteger(42));  // true
console.log(Number.isInteger(3.14)); // false