Find the Longest Word in a String using Reduce

Find the Longest Word in a String using Reduce


Can anyone explain why does my code not work? I can get it to log "jumped’ if I type “return prev” instead of “return prev.length” but I can’t get it to log 6.

function findLongestWord(str) {
return str.split(’ ').reduce(function (prev, curr) {
if (prev.length > curr.length) {
return prev.length;
} else {
return curr.length;

findLongestWord(“The quick brown fox jumped over the lazy dog”);


The first time the reduce function runs, prev is a string and has a .length property. But you return a number and prev becomes that number.

The next iteration of reduce is run and you try to get the value of prev.length - that’s a string property, not a number property.

If you stick to returning strings and then, when reduce is done, return the length of the reduce result, it should work fine.



The issue is that when you return prev.length you are returning a number. Javascript evaluates the number then as a string, with a length of one.

EDIT: Ah, beaten to the punch!


okay, gotcha. That makes sense.