spellchecker.js

const dict = ['computer', 'commuter', 'computation', 'computing', 'compute', 'computers'];
const letterDeletion = (word, index) => {
  if (index === 0) return false;
  let newWord = `${word.slice(0, index - 1)}${word.slice(index)}`;
  if (dict.find(w => w === newWord)) {
    return newWord;
  } else {
    return letterDeletion(word, index - 1);
  }
}

const letterTransposition = (word, index) => {
  if (index === 0) return false;
  let newWord = `${word.slice(0, index - 2)}${word[index-1]}${word[index-2]}${word.slice(index)}`;
  // console.log({ newWord })
  if (dict.find(w => w === newWord)) {
    return newWord;
  } else {
    return letterTransposition(word, index - 1);
  }
}

const letterDuplication = (word, index) => {
  if (index === 0) return false;
   let newWord = `${word.slice(0, index - 1)}${word[index-1]}${word[index-1]}${word.slice(index)}`;
  // console.log({ newWord });
   if (dict.find(w => w === newWord)) {
    return newWord;
  } else {
    return letterDuplication(word, index - 1);
  }
}
const letters = 'abcdefghijklmnopqrstuvwxyz';

const letterInsertion = (word, index) => {
  if (index === 0) return false;
  for(let i = 0; i < 26; i++) {
    let newWord = `${word.slice(0, index - 1)}${word[index-1]}${letters[i]}${word.slice(index)}`;
    // console.log({ newWord });
    if (dict.find(w => w === newWord)) return newWord;
  }
  return letterInsertion(word, index - 1);
}

function spellCheck(word) {
  const wordLength = word.length;
  let result = letterDeletion(word, wordLength);
  if (result) return result;
  result = letterTransposition(word, wordLength - 1);
  if (result) return result;
  result = letterDuplication(word, wordLength - 1);
  if (result) return result;
  result = letterInsertion(word, wordLength);
  if (result) return result;
  return word;
}

spellCheck('comuters')