What does console.log(0.1 + 0.2); output?

Console output

Why

JavaScript numbers are IEEE 754 64-bit floating point, which stores values in binary. Neither 0.1 nor 0.2 has an exact binary representation, so each is stored with a tiny error, and adding them produces 0.30000000000000004. For exact decimal math (like currency), use integers (cents) or a decimal library.