Get the number of times each string occurs in an Array

Question

function countWords(inputWords) {
var sortArray = inputWords.sort(function (idx1, idx2) { return idx1.localeCompare(idx2) });
var resultArray = [];
var counter = 1;

sortArray.reduce(function (total, currentValue) {
    if (total == currentValue)
        counter++;
    else {
        resultArray.push(counter);
        counter = 1;
    }
    return currentValue;
});

    return resultArray;
}
module.exports = countWords

So currently I'm trying to get the number of times each string occurs in an Array. I wrote the function above, but it seems that it has a bug.

PS: That is an exercise of https://nodeschool.io/ .. npm install -g functional-javascript-workshop . I have to use the reduce function and I'm not allowed to use any for/while loops

That was my input/output:

input:      [ 'ad', 'ad', 'ad', 'aliqua', 'aliquip', 'aute', 'consectetur', 'consequat', 'culpa', 'culpa', 'culpa', 'do', 'do', 'dolor', 'dolore', 'eiusmod', 'elit', 'esse', 'esse', 'est', 'et', 'et', 'ex', 'excepteur', 'excepteur', 'exercitation', 'exercitation', 'id', 'id', 'id', 'incididunt', 'labore', 'laborum', 'lorem', 'magna', 'minim', 'minim', 'minim', 'mollit', 'nostrud', 'nulla', 'pariatur', 'proident', 'qui', 'qui', 'reprehenderit', 'reprehenderit', 'sint', 'ullamco', 'velit' ]
submission: [ 3, 1, 1, 1, 1, 1, 3, 2, 1, 1, 1, 1, 2, 1, 2, 1, 2, 2, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 2, 2, 1, 1 ]

The workshop "says" that this is wrong.

Can somebody help?

_"The workshop "says" that this is wrong."_ What is "wrong"? Is the result actually incorrect? Have you checked the result? — guest271314, Jan 07 '17 at 22:15
The workshop check probably has a problem with the order of the results because of the `Array#sort`. — Ori Drori, Jan 07 '17 at 22:18
Possible duplicate of [Finding occurrences of a word in a string in python 3](http://stackoverflow.com/questions/17268958/finding-occurrences-of-a-word-in-a-string-in-python-3) — ppasler, Jan 07 '17 at 22:21
@guest271314 the result is wrong, otherwise I would pass the exercise — , Jan 07 '17 at 22:24
@TiZaLjubavNisiRodjena Did you check result? Where is result "wrong"? That is, how will you know when you have the correct answer? How do you know "exercise" is not "wrong"? What is expected result? — guest271314, Jan 07 '17 at 22:25
@guest271314input: It prints: # FAIL Your solution to Basic: Reduce didn't pass. Try again! — , Jan 07 '17 at 22:55
@TiZaLjubavNisiRodjena _"otherwise it will say pass"_ That is not an acceptable answer which would clarify expected result. What is "it"? — guest271314, Jan 07 '17 at 23:05
@guest271314 If my result is correct, then cmd prints : # PASS Your solution to Basic: Reduce passed! — , Jan 07 '17 at 23:07
@TiZaLjubavNisiRodjena That does not answer what is incorrect at `javascript` at Question. Do you know what is "wrong" or incorrect at `javascript` result at Question? — guest271314, Jan 07 '17 at 23:12

Ori Drori · Answer 1 · 2017-01-07T22:41:59.600

The workshop check probably has a problem with the order of the results you submitted, because of the Array#sort you use at the start of the function.

You can use these methods to count without changing the order of the results:

A ES6 word counter with Array#reduce that uses array spread syntax and Map. The Map counts the words. The Map is converted to an iterator by the Map#values, and then to an array using spread.

const words = [ 'ad', 'ad', 'ad', 'aliqua', 'aliquip', 'aute', 'consectetur', 'consequat', 'culpa', 'culpa', 'culpa', 'do', 'do', 'dolor', 'dolore', 'eiusmod', 'elit', 'esse', 'esse', 'est', 'et', 'et', 'ex', 'excepteur', 'excepteur', 'exercitation', 'exercitation', 'id', 'id', 'id', 'incididunt', 'labore', 'laborum', 'lorem', 'magna', 'minim', 'minim', 'minim', 'mollit', 'nostrud', 'nulla', 'pariatur', 'proident', 'qui', 'qui', 'reprehenderit', 'reprehenderit', 'sint', 'ullamco', 'velit' ];

const countWords = (words) => [...words.reduce((m, w) => m.set(w, (m.get(w) || 0) + 1), new Map).values()];

const result = countWords(words);

console.log(result);

And the ES5 version that uses Array#reduce with a hash object.

var words = [ 'ad', 'ad', 'ad', 'aliqua', 'aliquip', 'aute', 'consectetur', 'consequat', 'culpa', 'culpa', 'culpa', 'do', 'do', 'dolor', 'dolore', 'eiusmod', 'elit', 'esse', 'esse', 'est', 'et', 'et', 'ex', 'excepteur', 'excepteur', 'exercitation', 'exercitation', 'id', 'id', 'id', 'incididunt', 'labore', 'laborum', 'lorem', 'magna', 'minim', 'minim', 'minim', 'mollit', 'nostrud', 'nulla', 'pariatur', 'proident', 'qui', 'qui', 'reprehenderit', 'reprehenderit', 'sint', 'ullamco', 'velit' ];

function countWords(arr) {
  return words.reduce(function(m, w) {
    // if the hash doesn't include the word
    if (!m.hash.hasOwnProperty(w)) {
      // push a new count of 0 to that word
      m.counts.push(0)
      
      // add the index of the word's count
      m.hash[w] = m.counts.length - 1;
    }

    // increment the count at the index of the word's count
    m.counts[m.hash[w]]++;

    return m;
  }, { hash: {}, counts: [] }).counts; // return the counts array
}

var result = countWords(words);

console.log(result);

Get the number of times each string occurs in an Array

1 Answers1