String Palindrome Check in JavaScript

1// Method 1: Compare with reversed string
2function isPalindrome1(str) {
3    str = str.toLowerCase().replace(/[^a-z0-9]/g, '');
4    return str === str.split('').reverse().join('');
5}
6
7console.log("madam:", isPalindrome1("madam"));
8console.log("hello:", isPalindrome1("hello"));
9console.log("A man a plan:", isPalindrome1("A man a plan a canal Panama"));
10
11// Method 2: Two-pointer approach
12function isPalindrome2(str) {
13    str = str.toLowerCase().replace(/[^a-z0-9]/g, '');
14    let left = 0;
15    let right = str.length - 1;
16    
17    while (left < right) {
18        if (str[left] !== str[right]) {
19            return false;
20        }
21        left++;
22        right--;
23    }
24    return true;
25}
26
27console.log("\nTwo-pointer:");
28console.log("racecar:", isPalindrome2("racecar"));
29console.log("world:", isPalindrome2("world"));
30
31// Method 3: Recursive approach
32function isPalindrome3(str) {
33    str = str.toLowerCase().replace(/[^a-z0-9]/g, '');
34    
35    if (str.length <= 1) return true;
36    if (str[0] !== str[str.length - 1]) return false;
37    
38    return isPalindrome3(str.slice(1, -1));
39}
40
41console.log("\nRecursive:");
42console.log("level:", isPalindrome3("level"));
43console.log("hello:", isPalindrome3("hello"));
44
45// Method 4: Using every method
46function isPalindrome4(str) {
47    str = str.toLowerCase().replace(/[^a-z0-9]/g, '');
48    return str.split('').every((char, i) => {
49        return char === str[str.length - 1 - i];
50    });
51}
52
53console.log("\nUsing every:");
54console.log("deed:", isPalindrome4("deed"));