有没有办法找出字符串中某个单词之后是哪个单词？

function findNextWord(str, targetWord) {
  const words = str.split(' ');
  const targetIndex = words.indexOf(targetWord);

  if (targetIndex !== -1) {
    if (targetIndex < words.length - 1) {
      return words[targetIndex + 1];
    } else {
      return '目标单词之后没有下一个单词';
    }
  } else {
    return '目标单词不存在';
  }
}

const sentence = 'This is a sample sentence.';
const target = 'is';

const nextWord = findNextWord(sentence, target);
console.log(nextWord);