1var assert = require('assert');
2
3function findDuplicates(str) {
4  const dupes = [];
5  const strLowerCase = str.toLowerCase();
6  const strArr = strLowerCase.split(' ');
7  const wordFreqCounter = {};
8
9  strArr.forEach((word) => {
10    if (!wordFreqCounter[word]) {
11      wordFreqCounter[word] = 1;
12    } else {
13      wordFreqCounter[word] += 1;
14    }
15  });
16
17  let allKeys = Object.keys(wordFreqCounter);
18
19  allKeys.forEach((key) => {
20    if (wordFreqCounter[key] > 1) {
21      dupes.push(key);
22    }
23  });
24
25  return dupes;
26}
27
28try {
29  assert.deepEqual(findDuplicates('The dog is the best'), ['the']);
30
31  console.log(
32    'PASSED: ' + "`findDuplicates('The dog is the best')` returns `['the']`"
33  );
34} catch (err) {
35  console.log(err);
36}
37
38try {
39  assert.deepEqual(findDuplicates('Happy thanksgiving, I am so full'), []);
40
41  console.log(
42    'PASSED: ' +
43      "`findDuplicates('Happy thanksgiving, I am so full’)` returns `[]`"
44  );
45} catch (err) {
46  console.log(err);
47}