hangul.mjs

// @ts-check

// https://en.wikipedia.org/wiki/Korean_language_and_computers#Hangul_Syllables_block
const INITIAL = 'ᄀ'.charCodeAt(0)
const MEDIAL = 'ᅡ'.charCodeAt(0)
const FINAL = 'ᆨ'.charCodeAt(0) - 1

const initials = new Set()
const medials = new Set()
const finals = new Set()

console.info(charRange(0xAC00, 0xD7A3).map(check))

assert([...initials].join('') === 'ᄀᄁᄂᄃᄄᄅᄆᄇᄈᄉᄊᄋᄌᄍᄎᄏᄐᄑᄒ')
assert([...medials].join('') === 'ᅡᅢᅣᅤᅥᅦᅧᅨᅩᅪᅫᅬᅭᅮᅯᅰᅱᅲᅳᅴᅵ')
assert([...finals].join('') === 'ᆨᆩᆪᆫᆬᆭᆮᆯᆰᆱᆲᆳᆴᆵᆶᆷᆸᆹᆺᆻᆼᆽᆾᆿᇀᇁᇂ')

/** @param {string} char */
function check(char) {
	const cp = char.charCodeAt(0)
	const [initial, medial, final = null] = char.normalize('NFD')
	assert(initial != null)
	assert(medial != null)
	const calced = calculateCodePoint(initial, medial, final)
	initials.add(initial)
	medials.add(medial)
	if (final != null) finals.add(final)
	assert(calced === cp)
	return { char, initial, medial, final }
}

/**
 * @param {string} initial
 * @param {string} medial
 * @param {string | null} final
 */
function calculateCodePoint(initial, medial, final) {
	const i = initial.charCodeAt(0) - INITIAL
	const m = medial.charCodeAt(0) - MEDIAL
	const f = final == null ? 0 : final.charCodeAt(0) - FINAL

	return i * 588 + m * 28 + f + 44032
}

/**
 * @param {number} start
 * @param {number} end
 */
function charRange(start, end) {
	return Array.from({ length: end - start + 1 }, (_, i) => String.fromCodePoint(i + start))
}

/**
 * @param {boolean} condition
 * @returns {asserts condition}
 */
function assert(condition, message = 'Assertion failed') {
	if (!condition) throw new Error(message)
}