palindrome

amit265 · amit265 · commit 39b6426217fe · 2026-04-13T22:35:30.000+05:30
diff --git a/javascript/5_string-programs/palindrome.js b/javascript/5_string-programs/palindrome.js
@@ -0,0 +1,99 @@
+// 16. Check if String is Palindrome
+
+// Method 1: Naive Approach
+
+{
+  function check_palindrome(str) {
+    let j = str.length - 1;
+    for (let i = 0; i < j / 2; i++) {
+      let x = str[i];
+      let y = str[j - i];
+
+      if (x != y) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  function isPalindrome(str) {
+    let ans = check_palindrome(str);
+
+    if (ans == true) console.log(str + " is a palindrome");
+    else console.log(str + " not palindrome");
+  }
+
+  let test = "abaaba";
+  isPalindrome(test);
+
+  console.log(check_palindrome("jalaj"));
+}
+
+// Method 2: Reversing the string
+
+{
+  function reverse(str) {
+    let rev_str = "";
+    for (let i = str.length - 1; i >= 0; i--) {
+      rev_str += str[i];
+    }
+
+    return rev_str;
+  }
+
+  function isPalindrome(str) {
+    reverse_str = reverse(str);
+
+    if (reverse_str === str) {
+      console.log("passed string is palindrome");
+    } else {
+      console.log("passed string is not palindrome");
+    }
+  }
+
+  let test = "hellolleh";
+  isPalindrome(test);
+}
+
+// Method 3: Using the split(), reverse(), and join() Methods
+
+{
+  let check_palindrome = (str) => str === str.split("").reverse().join("");
+  console.log(check_palindrome("hellolleh"));
+}
+
+// Method 4: Using Array.every()
+
+{
+  function isPalindrome(str) {
+    return str
+      .split("")
+      .every((char, index) => char === str[str.length - index - 1]);
+  }
+
+  console.log(isPalindrome("radar"));
+  console.log(isPalindrome("hello"));
+  console.log(isPalindrome("level"));
+}
+
+//  Method 5: Using Two Pointers
+
+{
+  function isPalindrome(str) {
+    let left = 0;
+    let right = str.length - 1;
+
+    while (left < right) {
+      if (str[left] !== str[right]) return false;
+
+      left++;
+      right--;
+    }
+
+    return true;
+  }
+
+  console.log(isPalindrome("madam"));
+  console.log(isPalindrome("test"));
+  console.log(isPalindrome("abba"));
+}
