JavaScript: Check whether a passed string is palindrome or not

JavaScript Function: Exercise-2 with Solution

Check Palindrome

Write a JavaScript function that checks whether a passed string is a palindrome or not?

Note: A palindrome is word, phrase, or sequence that reads the same backward as forward, e.g., madam or nurses run.

Visual Presentation:

Sample Solution-1:

JavaScript Code:

 // Write a JavaScript function that checks whether a passed string is palindrome or not? 
function check_Palindrome(str_entry){
// Change the string into lower case and remove  all non-alphanumeric characters
   var cstr = str_entry.toLowerCase().replace(/[^a-zA-Z0-9]+/g,'');
	var ccount = 0;
// Check whether the string is empty or not
	if(cstr==="") {
		console.log("Nothing found!");
		return false;
	}
// Check if the length of the string is even or odd 
	if ((cstr.length) % 2 === 0) {
		ccount = (cstr.length) / 2;
	} else {
// If the length of the string is 1 then it becomes a palindrome
		if (cstr.length === 1) {
			console.log("Entry is a palindrome.");
			return true;
		} else {
// If the length of the string is odd ignore middle character
			ccount = (cstr.length - 1) / 2;
		}
	}
// Loop through to check the first character to the last character and then move next
	for (var x = 0; x < ccount; x++) {
// Compare characters and drop them if they do not match 
		if (cstr[x] != cstr.slice(-1-x)[0]) {
			console.log("Entry is not a palindrome.");
			return false;
		}
	}
	console.log("The entry is a palindrome.");
	return true;
}
check_Palindrome('madam');
check_Palindrome('nursesrun');
check_Palindrome('fox');

Output:

The entry is a palindrome.
The entry is a palindrome.
Entry is not a palindrome.

Flowchart:

Live Demo:

See the Pen JavaScript -Check whether a passed string is palindrome or not-function-ex- 2 by w3resource (@w3resource) on CodePen.

Sample Solution-2:

JavaScript Code:

// Define a function named isPalindrome that takes a string parameter (str)
function isPalindrome(str) {
  // Get the length of the string and store it in the constant variable len
  const len = str.length;

  // Iterate through the first half of the string
  for (let i = 0; i < len / 2; i++) {
    // Check if the character at position i is not equal to its corresponding character from the end
    if (str[i] !== str[len - 1 - i]) {
      // If not equal, return false as it is not a palindrome
      return false;
    }
  }

  // If the loop completes without returning false, the string is a palindrome, so return true
  return true;
}
// Declare constant variables str1, str2, and str3 with different string values
const str1 = 'madam';
const str2 = 'nursesrun';
const str3 = 'fox';

// Call the isPalindrome function for each string and log the result to the console
console.log(isPalindrome(str1)); 
console.log(isPalindrome(str2)); 
console.log(isPalindrome(str3)); 

Output:

true
true
false

Explanation:
The above function compares the characters at the beginning and end of the string. If the characters do not match, the function returns false. If all the characters match, the function returns true

Flowchart:

For more Practice: Solve these Related Problems:

• Write a JavaScript function that checks if a sentence is a palindrome, ignoring spaces, punctuation, and case.
• Write a JavaScript function that verifies whether a number is a palindrome without converting the number to a string.
• Write a JavaScript function that determines if an array of characters forms a palindrome.
• Write a JavaScript function that checks for a palindrome using a recursive approach.

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