返回字符串中最长单词的长度（JavaScript）

Question

Desired outcome is a the length of the longest word in a given string (numerical).

Ex: findLongestWord('I like tacos'); => 5

I get the 'cannot read length of undefined' error message when I start the loop from the end, and I only get the first new value of 'longest' when I start the loop forward. What am I missing?

function findLongestWord(string) {
  var longest = 0;
  var array = string.split(' ');
  for (var i = array.length; i >= 0; i--) {
    if (array[i].length > longest) {
        longest = array[i].length;
    }
  }
  return longest;
}

Answer 1

change your for to for (var i = array.length - 1; i >= 0; i--) {

if there 4 elements in array index start from 0 to 3 hence in that case array[4] is undefined

Answer 2

Your for loop first runs on i index which points to array.length that you're trying to access with the value of undefined .

Taken from MDN , Array length returns a 32-bit integer that is always numerically gerater than the highest index of the array.

In short, array.length is zero-based index.

So modifying your code to this will do,

function findLongestWord(string) {
  var longest = 0;
  var array = string.split(' ');
  for (var i = array.length - 1; i >= 0; i--) {
    if (array[i].length > longest) {
        longest = array[i].length;
    }
  }
  return longest;
}

But, here's another way you can achieve this...

function findLongestWord(str){
  var longestWord = '';
  str.split(' ').forEach(function (v) {
    longestWord = v.length > longestWord.length ? v : longestWord
  });
  return longestWord;
}

var word = findLongestWord('I like tacos');
console.log(longestWord, longestWord.length);
// tacos 5

Answer 3

array.length returns ,n, the number of elements in the array and when we fetch elements from the array using index it is from 0 to n-1. So you will have to use array.length -1 instead of array.length.

Answer 4

Using .sort will be easy .When you sorted array in DESC order ,get longest string by just index 0.

function findLongestWord(string) {       
  var array = string.split(' ');
  longest = array.sort(function(a,b){
      return a.length < b.length;
  });
  return longest[0].length;
  }

Answer 5

Thanks everybody for the great suggestions! I now see there are cleaner/shorter ways to handle this toy problem but I went with adding the 'length -1' to my loop, as that's the closest to what I had come up on my own.

Thanks!