1var assert = require('assert');
2
3function reverseOnlyAlphabetical(str) {
4  const alphaChars = [];
5  str = str.split(''); // strings are immutable in JS
6
7  for (let char of str) {
8    if (/[a-zA-Z]/.test(char)) {
9      alphaChars.push(char);
10    }
11  }
12
13  const reversedAlpha = reverseArray(alphaChars);
14
15  let idxRA = 0;
16  for (let i = 0; i < str.length; i++) {
17    if (/[a-zA-Z]/.test(str[i])) {
18      str[i] = reversedAlpha[idxRA++];
19    }
20  }
21
22  return str.join('');
23}
24
25function reverseArray(arr) {
26  let start = 0;
27  let end = arr.length - 1;
28
29  while (start <= end) {
30    const temp = arr[start];
31    arr[start] = arr[end];
32    arr[end] = temp;
33
34    start++;
35    end--;
36  }
37
38  return arr;
39}
40
41try {
42  assertIsFunction(
43    reverseOnlyAlphabetical,
44    'reverseOnlyAlphabetical is a function'
45  );
46
47  console.log('PASSED: ' + 'Expect `reverseOnlyAlphabetical` is a function');
48} catch (err) {
49  console.log(err);
50}
51
52try {
53  assert.equal(
54    reverseOnlyAlphabetical('sea!$hells3'),
55    'sll!$ehaes3',
56    "reverseOnlyAlphabetical('sea!$hells3') should equal 'sll!$ehaes3'"
57  );
58
59  console.log(
60    'PASSED: ' +
61      "Expect `reverseOnlyAlphabetical('sea!$hells3')` to return `'sll!$ehaes3'`"
62  );
63} catch (err) {
64  console.log(err);
65}
66
67try {
68  assert.equal(
69    reverseOnlyAlphabetical('1kas90jda3'),
70    '1adj90sak3',
71    "reverseOnlyAlphabetical('1kas90jda3') should return '1adj90sak3'"
72  );
73
74  console.log(
75    'PASSED: ' +
76      "Expect `reverseOnlyAlphabetical('1kas90jda3')` to return `'1adj90sak3'`"
77  );
78} catch (err) {
79  console.log(err);
80}
81
82function assertIsFunction(f) {
83  return typeof f === 'function';
84}