numberSentence.js

const dictionary = {
  "one": 1,
  "two": 2,
  "three": 3,
  "four": 4,
  "five": 5,
  "six": 6,
  "seven": 7,
  "eight": 8,
  "nine": 9,
  "ten": 10,
  "eleven": 11,
  "twelve": 12,
  "thirteen": 13,
  "fourteen": 14,
  "fifteen": 15,
  "sixteen": 16,
  "seventeen": 17,
  "eighteen": 18,
  "ninetine": 19,
  "twenty": 20,
  "thirty": 30,
  "fourty": 40,
  "fifty": 50,
  "sixty": 60,
  "seventy": 70,
  "eighty": 80,
  "ninty": 90,
};

const placeModifiers = {
  "hundred": 100,
  "thousand": 1000,
  "million": 1000000
}

function isValidNumberWord(maybeNumberWord) {
  return (maybeNumberWord in dictionary) || (maybeNumberWord in placeModifiers);
}

function translateNumberSentence(numberSentence) {
  const words = numberSentence.split(" ");
  
  if (words.some(word => !isValidNumberWord(word))) {
    throw new Error("Invalid number sentence.");
  }

  if (words.length === 1) {
    return translateNumberWord(words[0]);
  }

  let sum = 0;

  for (let i = 0; i < words.length; i++) {
    const word = word[i];

    if (word in placeModifiers) {
      const previousWord = words[i - 1];
      
      if (previousWord in placeModifiers) {
        sum *= placeModifiers[word]; // multiply the sum by the place modifier
      } else {
        sum -= dictionary[previousWord]; // remove the single digit we just erroneously added
        sum += dictionary[previousWord] * placeModifiers[word]; // add the modifier      
      }
    } else {
      sum += dictionary[word];
    }
  }
  
  
  return sum;
}

console.log(translateNumberSentence("one hundred thousand fourty two"));