Update palindrome.js

Author: BuildWithLal

algorithms/palindrome.js

@@ -1,19 +1,27 @@
 function isPalindrome(str){
 
-    let isPalindrome = true;
+    const validChars = 'abcdefghijklmnopqrstuvwxyz';
+    const validCharsArr = validChars.split("");
+    const strArr = str.split("");
 
-    for (let i=0; i < str.length; i++){
+    const newStrArr = strArr.filter(char => validCharsArr.indexOf(char) !== -1);
+    console.log(newStrArr);
+    
+    return newStrArr.join("") === newStrArr.reverse().join("");
+    
+    
+    /*
+        without using array functions i.e join() and reverse()
         
-       
-       if (str[i] === str[str.length - (i+1)]) continue;
-       
-       else isPalindrome = false;
+        let isPalindrome = true;
+        for (let i=0; i < newStrArr.length; i++){
+           if (newStrArr[i] === newStrArr[newStrArr.length - (i+1)]) continue;
+           else isPalindrome = false;
+        }
         
-    }
-    
-    return isPalindrome;
+        return isPalindrome;
+    */        
 
 }
 
-isPalindrome('madam');
-isPalindrome('shot');
+isPalindrome('lalal');