Split Thai graphemes but fix for vertical display

thai-split.js

function splitthai(str) {
  // https://github.com/nota/split-graphemes/blob/master/src/thai.js
  const letter = '[\\u0E00-\\u0E7F]';
  const trailingLetter = '[\\u0E31\\u0E33-\\u0E3A\\u0E47-\\u0E4E]';
  const thai = `${letter}${trailingLetter}*`;
  const splitter = new RegExp(`(${thai})`, 'gu');

  return str.replace(/ำ/g, 'ํา').replace(/แ/g, 'เเ').match(splitter) || [];
}

console.log(splitthai('อิอิกำ')); // [ 'อิ', 'อิ', 'กํ', 'า' ]
console.log(splitthai('ไม้ทัณฑฆาต')); // ['ไ', 'ม้', 'ทั', 'ณ', 'ฑ', 'ฆ', 'า', 'ต'])
console.log(splitthai('ข้าวมันไก่')); // ['ข้', 'า', 'ว', 'มั', 'น', 'ไ', 'ก่'])
console.log(splitthai('ลำแสง')); // [ 'ลํ', 'า', 'เ', 'เ', 'ส', 'ง' ]