Javascript: Check if Input is Palindrome

Sep 4, 2014
I had a past post about how to check if input is palindrome in C#.

This one is another Javascript exercise with the same goal.

-create a function that determines the string input as palindrome
-use arrays and loops to check if the string is a palindrome (try reading .split and join function, DO NOT USE REVERSE FUNCTION in javascript)
-use text box to for string input
-use button to determine output
-insert text "is a palindrome" below the text box if string is a palindrome else "not a palindrome" --> use ternary operator for this

Here is my solution.


<!DOCTYPE html>
  <script type="text/javascript" src="palindrome.js">
  <input type="text" id="input_text"></input>
  <button onClick="isPalindrome()">Check</button>
  <br />
  <label id="output_text"></label>


function isPalindrome(){
 var inputString = document.getElementById("input_text").value.toLowerCase();
 var revString = [];
 inputString = inputString.replace(/[^a-zA-Z-]/g, ''); //removes all non-alphabet letters, including white space;
 for(var indx = inputString.length-1; indx >= 0; indx--){
 revString = revString.join('');
 document.getElementById("output_text").innerHTML = ""; //set to empty; to 'delete' any value already existing in the node;
 document.getElementById("output_text").innerHTML += (inputString === revString) ? "is a palindrome" : "not a palindrome";


For clarifications and/or better solutions, please feel free to leave a message on the comments section.

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