What is 0.1 + 0.2 in JavaScript? Why? How to avoid floating-point issues?

Result of 0.1 + 0.2

0.1 + 0.2 === 0.3 // false
0.1 + 0.2         // 0.30000000000000004

Why?

JavaScript uses IEEE 754 double-precision floats. Neither 0.1 nor 0.2 can be represented exactly in binary, causing rounding errors when added.

Solutions

1. Epsilon comparison

Math.abs(0.1 + 0.2 - 0.3) < Number.EPSILON // true

2. Integer arithmetic

(0.1 * 10 + 0.2 * 10) / 10 // 0.3

3. toFixed()

parseFloat((0.1 + 0.2).toFixed(10)) // 0.3

4. Use a library

Use decimal.js or big.js for arbitrary precision.