Build a Palindrome Checker - Run the Tests

JavaScript
1

Run the Tests button returns failure on working JavaScript. Below JavaScript works fine on the all test cases. You can test this code on your side.

const textInput = document.getElementById(“text-input”);
const checkBtn = document.getElementById(“check-btn”);
const result = document.getElementById(“result”);

checkBtn.addEventListener(“click”, () => {
let isPalindrome = true;
let alphaNumericString = new String(textInput.value).trim().toLowerCase().replace(/[^a-zA-Z0-9]/g,“”);
if (alphaNumericString.length == 0) {
alert(“Please input a value”);
} else {
for (i = 0; i < alphaNumericString.length / 2; i++) {
if(alphaNumericString[i] != alphaNumericString[alphaNumericString.length - i - 1]) {
isPalindrome = false;
break;
}
}
result.innerText = isPalindrome ? textInput.value + " is a palindrome" : textInput.value + " is not a palindrome";
}
});

Palindrome Test

Enter

body {
background-color: black;
color: white;
}

This is very simple as you see but the ‘Run the Tests’ buttonn fails to test this code.

2

Welcome to the forum @hsyeon01

Please post your html code as well so the forum can assist.

Happy coding

10

Hi @hsyeon01

The i variable in the for loop needs to be declared.

Thanks for posting the html code in the correct format.

Happy coding

11 
<!DOCTYPE html>
 <html>
    <head>
        <link rel="stylesheet" href="./styles.css" />
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
    </head>
    <body>
        <h1>Palindrome Test</h1>
        <p>     
            <input type="text" id="text-input">
            <button type="button" id="check-btn">Enter</button>
            <div id="result">            
            </div>
        </p>
        <script src="./script.js"></script>
    </body>
 </html>```
12

Thanks but why this js works without any error without ‘let’ in for loop?

13

If you omit declaring a variable you are implicitly creating a global variable.
Good practice is to declare variable scope.

Happy coding

14

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