【JavaScript】半角カタカナ、全角カタカナ、ひらがなへの変換

const HALF_KATA = [
	'ｧ','ｱ','ｨ','ｲ','ｩ','ｳ','ｪ','ｴ','ｫ','ｵ',
	'ｶ','ｶﾞ','ｷ','ｷﾞ','ｸ','ｸﾞ','ｹ','ｹﾞ','ｺ','ｺﾞ',
	'ｻ','ｻﾞ','ｼ','ｼﾞ','ｽ','ｽﾞ','ｾ','ｾﾞ','ｿ','ｿﾞ',
	'ﾀ','ﾀﾞ','ﾁ','ﾁﾞ','ｯ','ﾂ','ﾂﾞ','ﾃ','ﾃﾞ','ﾄ','ﾄﾞ',
	'ﾅ','ﾆ','ﾇ','ﾈ','ﾉ',
	'ﾊ','ﾊﾞ','ﾊﾟ','ﾋ','ﾋﾞ','ﾋﾟ','ﾌ','ﾌﾞ','ﾌﾟ','ﾍ','ﾍﾞ','ﾍﾟ','ﾎ','ﾎﾞ','ﾎﾟ',
	'ﾏ','ﾐ','ﾑ','ﾒ','ﾓ',
	'ｬ','ﾔ','ｭ','ﾕ','ｮ','ﾖ',
	'ﾗ','ﾘ','ﾙ','ﾚ','ﾛ',
	'ヮ','ﾜ','ヰ','ヱ','ｦ','ﾝ','ｳﾞ','ヵ','ヶ','ﾜﾞ','ｲﾞ','ｴﾞ','ｦﾞ'
]

const halfKataToWide = (text, hira=false) => {
	const firstCharCode = hira === true ? 12353 : 12449
	return text.replace(/[ﾜｲｴｦ]ﾞ/g, m => 
			'ヷヸヹヺ'.charAt('ﾜﾞｲﾞｴﾞｦﾞ'.indexOf(m) / 2)
		).replace(/([ｦ-ｯｱｲｴｵﾅ-ﾉﾏ-ﾝ]|[ｳｶ-ﾄ]ﾞ?|[ﾊ-ﾎ][ﾞﾟ]?)/g, m => 
			String.fromCharCode(HALF_KATA.indexOf(m) + firstCharCode)
		).replace(/[ﾞﾟｰ｡｢｣､･]/g, m => 
			'゛゜ー。「」、・'.charAt('ﾞﾟｰ｡｢｣､･'.indexOf(m))
		)
}

const toHira = (text) => 
	halfKataToWide(text, true).replace(/[ァ-ヶ]/g, m => String.fromCharCode(m.charCodeAt(0) - 0x60))

const toWideKata = (text) => 
	halfKataToWide(text).replace(/[ぁ-ゖ]/g, m => String.fromCharCode(m.charCodeAt(0) + 0x60))

const toHalfKata = (text) => 
	text.replace(/[ァ-ヺ]/g, m => HALF_KATA[m.charCodeAt(0) - 12449])
		.replace(/[ぁ-ゖ]/g, m => HALF_KATA[m.charCodeAt(0) - 12353])
		.replace(/[゛゜ー。「」、・]/g, m => 'ﾞﾟｰ｡｢｣､･'.charAt('゛゜ー。「」、・'.indexOf(m)))


const str = 'ひびぴヒビピﾋﾋﾞﾋﾟゐゑをんゔゕゖﾝﾞﾟｦﾞﾟｰ｡｢｣､･゛゜ー。「」、・'
console.log(toHira(str))
			//ひびぴひびぴひびぴゐゑをんゔゕゖん゛゜ヺ゜ー。「」、・゛゜ー。「」、・
console.log(toWideKata(str))
			//ヒビピヒビピヒビピヰヱヲンヴヵヶン゛゜ヺ゜ー。「」、・゛゜ー。「」、・
console.log(toHalfKata(str))
			//ﾋﾋﾞﾋﾟﾋﾋﾞﾋﾟﾋﾋﾞﾋﾟヰヱｦﾝｳﾞヵヶﾝﾞﾟｦﾞﾟｰ｡｢｣､･ﾞﾟｰ｡｢｣､･

自分でまとめた変換用のclass構文からメソッドを抜き出して再構築したものです。