JavaScript Program to Check Whether a String is Palindrome or Not

Introduction

A palindrome is a word, phrase, number, or other sequences of characters that reads the same forward and backward, ignoring spaces, punctuation, and capitalization. Checking if a string is a palindrome is a popular problem in computer science and programming interviews.

In this article, you will learn how to check whether a string is a palindrome using JavaScript. You'll explore multiple examples that demonstrate how to implement this function and discuss improvements to handle edge cases effectively.

Basic Palindrome Check

Implementing a Simple Palindrome Function

1. Create a function to reverse the input string.

2. Compare the original string with the reversed string to determine if it's a palindrome.

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   function isPalindrome(str) {
       const reversed = str.split('').reverse().join('');
       return str === reversed;
   }

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   This function splits the string into an array of characters, reverses that array, and joins the characters back into a string. It then compares this string to the original string.

Examples of Basic Palindrome Check

1. Test the function with a palindrome.

2. Test the function with a non-palindrome.

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   console.log(isPalindrome('racecar'));  // Output: true
   console.log(isPalindrome('hello'));    // Output: false

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   Here, 'racecar' reads the same backward and forward, whereas 'hello' does not.

Advanced Palindrome Check

Handling Case Sensitivity and Non-Alphanumeric Characters

1. Modify the original function to convert the string to lowercase.

2. Use a regular expression to remove non-alphanumeric characters.

   JAVASCRIPT

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   function isAdvancedPalindrome(str) {
       const cleaned = str.toLowerCase().replace(/[\W_]/g, '');
       const reversed = cleaned.split('').reverse().join('');
       return cleaned === reversed;
   }

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   This version of the function first converts the entire string to lowercase and removes any characters that aren't letters or numbers. It then checks if the cleaned, reversed string is a palindrome.

Examples of Advanced Palindrome Check

1. Test the function with a complex string including spaces and punctuation.

2. Test the function with mixed cases.

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   console.log(isAdvancedPalindrome('A man, a plan, a canal: Panama'));  // Output: true
   console.log(isAdvancedPalindrome('No lemon, no melon'));             // Output: true

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   These strings, when spaces and punctuation are removed and the case is normalized, read the same backward as forward.

Conclusion

By following the examples above, you can effectively determine if a string is a palindrome in JavaScript. Starting from a basic implementation to more advanced checks that handle cases and non-alphanumeric characters, these techniques ensure that your function is robust and handles a wider range of inputs. Use these methods in your projects to efficiently handle string evaluation tasks relating to palindromes.