The unicorn emoji 🦄 is 1 code point (0x0001f984), 2 code units in UTF-16 (0xd83e, 0xdd84), and 4 bytes in UTF-16 (0xd8, 0x3e, 0xdd, 0x84). The answer is different for encodings like UTF-8 or UTF-32 (JSON is UTF-16). And there is a whole separate ball of complexity around grapheme clusters.
