Why 0.1 + 0.2 Isn't 0.3 in JavaScript (Explained Simply)

Type 0.1 + 0.2 into JavaScript and you get 0.30000000000000004. It's not a bug: it's how computers store decimal numbers (IEEE 754, 64-bit floating point), and Python and PHP do exactly the same.

What you'll learn: why 0.1 can't be stored exactly in binary, why tiny rounding errors show up when you add, why it breaks code like if (total === 0.3), and 3 fixes: compare with a tolerance (Number.EPSILON), keep money in whole cents/paise, and round only for display with toFixed().

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Every result on screen was run for real: Node.js, Python 3 and PHP 8.3. Narration: Kokoro TTS (Apache-2.0). Music: original score. Animation: original.