Problems › JavaScript › patterns
Mirror text, ignoring the clutter
An audit tool checks whether a phrase reads the same forwards and backwards once the formatting — spaces, punctuation, digits — is stripped away.
- Only letters and digits count; everything else is ignored.
- The comparison is case-insensitive: “A” and “a” are the same.
- A phrase with nothing countable left is a palindrome.
isCleanPalindrome(text: string) → bool
Where you start
function isCleanPalindrome(text) {
}Worked examples
| Call | Result |
|---|---|
isCleanPalindrome("race a car") | false |
isCleanPalindrome("A man, a plan, a canal: Panama") | true |
isCleanPalindrome("racecar") | true |
isCleanPalindrome(" ") | true |
Hint
Walk from both ends at once, skipping anything that is not a letter or digit, and compare the survivors.
Reference solution in JavaScript
function isCleanPalindrome(text) {
let i = 0, j = text.length - 1;
while (i < j) {
const a = text[i], b = text[j];
if (!/[a-zA-Z0-9]/.test(a)) { i++; continue; }
if (!/[a-zA-Z0-9]/.test(b)) { j--; continue; }
if (a.toLowerCase() !== b.toLowerCase()) return false;
i++; j--;
}
return true;
}