Can't spell a thing without this other thing

gistfile1.txt

function makeTweet(bot){
  var tweet = "";
  var subWord = "";
  
  while (subWord == ""){
    var word = getRandomWord(); //get random word from Wordnik API
    var startIndex = 1;   //starting with second letter in word, search for
    var endIndex = 5;     //all 4+ letter substrings for new words
    var possibleWords = [];
    while (startIndex <= word.length - 4 && endIndex <= word.length){
      var testString = word.slice(startIndex, endIndex);
      if (words.indexOf(testString) != -1){ //search list of scrabble words for substring words
        possibleWords.push(testString);
      }
      endIndex ++;
      if (endIndex == word.length+1){
        startIndex ++;
        endIndex = startIndex + 4;
      }
    }
    if (possibleWords.length > 0){
      subWord = randomChoice(possibleWords);
    }
  }
  
  tweet = "Can't spell "+word+" without "+subWord+".";
    
  tweet = encodeString(tweet); //URI-encodes tweet for HTTP post request
  return tweet;
}