JS: Char to UTF-16 Encoding 📜

Here is a function that return the hexadecimal string of UTF-16 Encoding of a unicode character's codepoint.

/*
xah_codepoint_to_utf16_hexStr(zcodepoint) return a string of hexadecimal that's the UTF-16 encoding of the char of codepoint zcodepoint (integer).
The result string is not padded, but one space is inserted to separate the first 2 bytes and last 2 bytes. Digits are in CAPITAL case.

URL http://xahlee.info/js/js_utf-16_encoding.html
Version: 2026-01-29
*/

const xah_codepoint_to_utf16_hexStr = (zcodepoint) =>
 ((xstr) => (Array.from(Array(xstr.length).keys(), (x) => (xstr.charCodeAt(x).toString(16).toUpperCase())).join(" ")))(String.fromCodePoint(zcodepoint));

// s------------------------------
// test

// 🦋
console.assert(xah_codepoint_to_utf16_hexStr(129419) === "D83E DD8B");

/*
🦋
BUTTERFLY
ID 129419
UTF16 D83E DD8B
*/

// A, codepoint 65, UTF16 41
console.assert(xah_codepoint_to_utf16_hexStr(65) === "41");