Stop Letting JavaScript Numbers Fool You – Master Them in Minutes!

title: "Understanding Numbers in JavaScript: A Complete Guide" description: "From floating-point quirks to BigInt, learn how numbers really work in JavaScript with examples and best practices." tags: javascript, webdev, beginners, programming JavaScript is a powerful and flexible language, but its handling of numbers can be a bit quirky—especially if you're coming from languages like Python or Java. In this article, we’ll break down how numbers work in JavaScript — from basic arithmetic to edge cases you should know. What Is a Number in JavaScript? In JavaScript, all numbers are stored as floating-point values, even if they look like integers. console.log(typeof 10); // "number" console.log(typeof 10.5); // "number" JavaScript uses the IEEE 754 double-precision floating-point format. Basic Arithmetic let a = 5; let b = 2; console.log(a + b); // 7 console.log(a - b); // 3 console.log(a * b); // 10 console.log(a / b); // 2.5 console.log(a % b); // 1 (modulus) All standard math operations work as expected. Number Quirks to Watch Out For 1. Floating Point Precision console.log(0.1 + 0.2); // 0.30000000000000004 Due to how binary floating-point math works, some numbers can’t be represented exactly. 2. Comparing Floats console.log(0.1 + 0.2 === 0.3); // false Instead, compare using a small threshold: const epsilon = Number.EPSILON; console.log(Math.abs((0.1 + 0.2) - 0.3)

May 3, 2025 - 16:04

Stop Letting JavaScript Numbers Fool You – Master Them in Minutes!

title: "Understanding Numbers in JavaScript: A Complete Guide"

description: "From floating-point quirks to BigInt, learn how numbers really work in JavaScript with examples and best practices."
tags: javascript, webdev, beginners, programming

JavaScript is a powerful and flexible language, but its handling of numbers can be a bit quirky—especially if you're coming from languages like Python or Java. In this article, we’ll break down how numbers work in JavaScript — from basic arithmetic to edge cases you should know.

What Is a Number in JavaScript?

In JavaScript, all numbers are stored as floating-point values, even if they look like integers.

console.log(typeof 10);       // "number"
console.log(typeof 10.5);     // "number"

JavaScript uses the IEEE 754 double-precision floating-point format.

Basic Arithmetic

let a = 5;
let b = 2;

console.log(a + b); // 7
console.log(a - b); // 3
console.log(a * b); // 10
console.log(a / b); // 2.5
console.log(a % b); // 1 (modulus)

All standard math operations work as expected.

Number Quirks to Watch Out For

1. Floating Point Precision

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

Due to how binary floating-point math works, some numbers can’t be represented exactly.

2. Comparing Floats

console.log(0.1 + 0.2 === 0.3); // false

Instead, compare using a small threshold:

const epsilon = Number.EPSILON;
console.log(Math.abs((0.1 + 0.2) - 0.3) < epsilon); // true

Special Number Values

JavaScript includes some special number values:

Infinity
-Infinity
NaN (Not a Number)

console.log(1 / 0);     // Infinity
console.log(-1 / 0);    // -Infinity
title: "Understanding Numbers in JavaScript: A Complete Guide"

description: "From floating-point quirks to BigInt, learn how numbers really work in JavaScript with examples and best practices."
tags: javascript, webdev, beginners, programming

JavaScript is a powerful and flexible language, but its handling of numbers can be a bit quirky—especially if you're coming from languages like Python or Java. In this article, we’ll break down how numbers work in JavaScript — from basic arithmetic to edge cases you should know.

---

## What Is a Number in JavaScript?

In JavaScript, **all numbers are stored as floating-point values**, even if they look like integers.

js
console.log(typeof 10); // "number"
console.log(typeof 10.5); // "number"


JavaScript uses the **IEEE 754 double-precision** floating-point format.

---

## Basic Arithmetic

js
let a = 5;
let b = 2;

console.log(a + b); // 7
console.log(a - b); // 3
console.log(a * b); // 10
console.log(a / b); // 2.5
console.log(a % b); // 1 (modulus)


All standard math operations work as expected.

---

## Number Quirks to Watch Out For

### 1. Floating Point Precision

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


Due to how binary floating-point math works, some numbers can’t be represented exactly.

### 2. Comparing Floats

js
console.log(0.1 + 0.2 === 0.3); // false


Instead, compare using a small threshold:

js
const epsilon = Number.EPSILON;
console.log(Math.abs((0.1 + 0.2) - 0.3) < epsilon); // true


---

## Special Number Values

JavaScript includes some special number values:

* `Infinity`
* `-Infinity`
* `NaN` (Not a Number)

js
console.log(1 / 0); // Infinity
console.log(-1 / 0); // -Infinity