Getting an array with lengths of words from a sentence -javascript

Question

I'm trying to create a function that will tell me how long the longest word in a sentence is. My approach is to split the sentence into strings of words. I now have an array of strings. My problem is that I want to use this array to get another array of numbers i.e. the length of each word. How do I do this? My code is as below but I keep getting null.

function findLongestWord(str) {
  var split = str.split(" ");
  for (j = 0; j < split.length; j++)
  var wordCount = split[j].length;
  var lengths = [];
  for (var i = 0; i < wordCount.length; i++) {
    lengths.push(i);
  }

  return Math.max(...lengths);
}

Answer 1

If you are going to loop through all the words you can already find the max (longest) word in your input array.

function findLongestWord(str) {
  var split = str.split(" ");
  var maxLength = 0;
  var longestWord = "";  // If no word is found "".length will return 0
  var len = split.length;
  for (j = 0; j < len; j++)
  {
    if (split[j].length > maxLength)
    {
        longestWord = split[j];
        maxLength = split[j].length;
    }
  }

  return longestWord;
}

And the returned value .length to get the length (or return maxLength if you so desire).

Note depending on your application punctuation might interfere with your algorithm.

Answer 2

I've made some comments about the mistakes in your code

function findLongestWord(str) {

  // better use .split(/\s+/) instead to remove trailing space in the middle of sentence
  var split = str.split(" ");
  
  // this for loop is redundant, you have to wrap the code that you want to loop with curly brackets.
  for (j = 0; j < split.length; j++)
  
  // the value of j would be the length of split array.
  var wordCount = split[j].length;
  var lengths = [];
  
  // since wordCount.length is undefined, so loop never gets excuted and your lengths array would be empty. 
  for (var i = 0; i < wordCount.length; i++) {
    lengths.push(i);
  }
  
  // doing Math.max on empty array will return -Infinity
  return Math.max(...lengths);
}

findLongestWord('hello there mate')

Below are my solutions. There are also more ways of doing what you want to do.

function findLongestWord(str) {
  // trim trailing white space.
  var split = str.trim().split(/\s+/);
  var lengths = [];
  
  // loop through array of words
  for (j = 0; j < split.length; j++) {
  
    // check the length of current words
    var wordCount = split[j].length;
    lengths.push(wordCount);
  }
  
  return Math.max(...lengths);
}

const sentence = 'hello its a me mariooooooo';

console.log(findLongestWord(sentence))

// one liner - using reduce function
const findLongestWord2 = (str) => str.trim().split(/\s+/).reduce((a, b) => a.length > b.length ? a.length : b.length, -Infinity);

console.log(findLongestWord2(sentence))

// less efficient but shorter - using sort
const findLongestWord3 = (str) => str.trim().split(/\s+/).sort((a, b) => a.length - b.length).pop().length;

console.log(findLongestWord3(sentence))

Answer 3

Create a function that takes an array of words and transforms it into an array of each word's length.

function multi(arr) {
     var newarr = [];
  for (var i = 0; i < arr.length; i++) {
      newarr.push( arr[i].length);
  }
  return newarr;
}

Answer 4

You need to use var to create j in the first for loop like you did for the second for loop with i.

Answer 5

This can be done using the .map() method. You map the array of strings into an array of word lengths, and then return the Math.max() of the array of lengths, like so:

function findLongestWord(str) {
  // map words into array of each word's length, grab highest #
  return Math.max(...str.split(" ").map(str => str.length));
}

console.log(findLongestWord("The quick brown fox jumped over the lazy dog"));