added palindrome checker Java

Programming/JavaScript/Check_Palindrome.js

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+function isPalindrome(str) {
+  // Convert to lower case and replace
+  // any non - alpha or digit character with empty string.
+  str = str.toLowerCase().replace(/[^a-z\d]/g, '');
+
+  //Now by 2 pointer approach by making pointers at initial position and end position
+  // either they meet or pass each other.
+  for (let i = 0, j = str.length - 1; i < j; i++, j--) {
+    if (str[i] !== str[j]) return false;
+  }
+
+  // If the loop completed with no issues,
+  // the string is a valid palindrome.
+  return true;
+}
+
+//Example - String is 'race a car':
+//Output : False
+
+//Example - String is 'madam';
+//Output : True
+
+//Time Complexity:
+//Best ,Worst and Average complexity : O(n)
+
+//Space Complexity:
+//Space Complexity of above program : O(1)