JavaScript: Check whether a passed string is palindrome or not

JavaScript Function: Exercise-2 with Solution

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.

Pictorial 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');

Sample 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.

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Sample Solution-2:

JavaScript Code:

function isPalindrome(str) {
  const len = str.length;
  for (let i = 0; i < len / 2; i++) {
    if (str[i] !== str[len - 1 - i]) {
      return false;
    }
  }
  return true;
}
const str1 = 'madam';
const str2 = 'nursesrun';
const str3 = 'fox';
console.log(isPalindrome(str1)); 
console.log(isPalindrome(str2)); 
console.log(isPalindrome(str3));

Sample 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:

Live Demo:

See the Pen javascript-function-exercise-2-1 by w3resource (@w3resource) on CodePen.

Improve this sample solution and post your code through Disqus

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