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‎README.md

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@@ -2125,3 +2125,50 @@ const toCamel = obj => {
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**[⬆ Back to Top](#javascript-coding-challenges-for-beginners)**
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## 59. Valid Palindrome
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A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forward and backward. Alphanumeric characters include letters and numbers. Given a string `s`, return `true` if it is a palindrome, or `false` otherwise.
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```js
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const isPalindrome = s => {
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// Your solution
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};
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console.log(isPalindrome('A man, a plan, a canal: Panama')); // true
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// Explanation: "amanaplanacanalpanama" is a palindrome.
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console.log(isPalindrome('race a car')); // false
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// Explanation: "raceacar" is not a palindrome.
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console.log(isPalindrome('ab_a')); // true
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// Explanation: "aba" is a palindrome.
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console.log(isPalindrome(' ')); // true
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// Explanation: `s` is an empty string "" after removing non-alphanumeric characters.
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// Since an empty string reads the same forward and backward, it is a palindrome.
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```
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<details><summary>Solution</summary>
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```js
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const isPalindrome = s => {
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const str = s.toLowerCase().replace(/[^a-z0-9]/g, '');
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let start = 0;
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let end = str.length - 1;
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while (start < end) {
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if (str[start] !== str[end]) return false;
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start++;
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end--;
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}
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return true;
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// Alternative solution using built-in reverse() method
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// const str = s.toLowerCase().replace(/[^a-z0-9]/g, '');
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// return str === [...str].reverse().join('');
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};
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```
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</details>
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---
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**[⬆ Back to Top](#javascript-coding-challenges-for-beginners)**

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