1var assert = require('assert');
2
3const longestPalindrome = (str) => {
4  if (!str || str.length <= 1) {
5    return str;
6  }
7
8  let longest = str.substring(0, 1);
9  for (let i = 0; i < str.length; i++) {
10    let temp = expand(str, i, i);
11    if (temp.length > longest.length) {
12      longest = temp;
13    }
14    temp = expand(str, i, i + 1);
15    if (temp.length > longest.length) {
16      longest = temp;
17    }
18  }
19  return longest;
20};
21
22const expand = (str, begin, end) => {
23  while (begin >= 0 && end <= str.length - 1 && str[begin] === str[end]) {
24    begin--;
25    end++;
26  }
27  return str.substring(begin + 1, end);
28};
29
30try {
31  assert.equal(longestPalindrome(''), '');
32
33  console.log('PASSED: ' + "`longestPalindrome('')` should return `''`");
34} catch (err) {
35  console.log(err);
36}
37
38try {
39  assert.equal(longestPalindrome('algodaily'), 'a');
40
41  console.log(
42    'PASSED: ' + "`longestPalindrome('algodaily')` should return `'a'`"
43  );
44} catch (err) {
45  console.log(err);
46}
47
48try {
49  assert.equal(longestPalindrome('gymmyg'), 'gymmyg');
50
51  console.log(
52    'PASSED: ' + "`longestPalindrome('gymmyg')` should return `'gymmyg'`"
53  );
54} catch (err) {
55  console.log(err);
56}
57
58try {
59  assert.equal(longestPalindrome('nasduhuuhdousan'), 'huuh');
60
61  console.log(
62    'PASSED: ' + "`longestPalindrome('nasduhuuhdousan')` should return `'huuh'`"
63  );
64} catch (err) {
65  console.log(err);
66}