I have a function that finds the longest word in a string.

function findLongestWord(str) {
  var longest = str.split(' ').reduce((longestWord, currentWord) =>{
    return currentWord.length > longestWord.length ? currentWord : longestWord;
  }, "");
  return longest;
}
console.log(findLongestWord("The quick brown fox jumped over the lazy dog"));

I'm having a hard time converting this to find the shortest word. Why can't I just change currentWord.length > longestWord.length to currentWord.length < longestWord.length?

I have a function that finds the longest word in a string.

function findLongestWord(str) {
  var longest = str.split(' ').reduce((longestWord, currentWord) =>{
    return currentWord.length > longestWord.length ? currentWord : longestWord;
  }, "");
  return longest;
}
console.log(findLongestWord("The quick brown fox jumped over the lazy dog"));

I'm having a hard time converting this to find the shortest word. Why can't I just change currentWord.length > longestWord.length to currentWord.length < longestWord.length?

• javascript
• arrays
• ecmascript-6
• reduce

• 2 The problem is the initial value "". You'll never find a word shorter than that. – Barmar Commented Mar 6, 2018 at 5:52
• ah ok, yes that makes sense – jdev99 Commented Mar 6, 2018 at 5:53

3 Answers 3

You need to provide an initial value to the reduce function, otherwise a blank string is the shortest word:

function findShortestWord(str) {
  var words = str.split(' ');
  var shortest = words.reduce((shortestWord, currentWord) => {
    return currentWord.length < shortestWord.length ? currentWord : shortestWord;
  }, words[0]);
  return shortest;
}
console.log(findShortestWord("The quick brown fox jumped over the lazy dog"));

While using reduce, initialValue is optional and if it isn't provided then your first element will be used as initialValue. So, in your case, you'll just have to remove your "":

function findLongestWord(str) {
  var longest = (typeof str == 'string'? str : '')
    .split(' ').reduce((longestWord, currentWord) =>{
      return currentWord.length < longestWord.length ? currentWord : longestWord;
  });
  return longest;
}
console.log(findLongestWord("The quick brown fox jumped over the lazy dog")); // The

I coded it in this way

const findLongestWord = str => {
  return typeof str === 'string' 
  ? str.split(' ').reduce((sw, lw) => lw.length < sw.length ? lw :sw)
  : '';
}
console.log(findLongestWord('The quick brown fox jumps over the lazy dog.')); //'The'