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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 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:

JavaScript: Check whether a passed string is palindrome or not

Sample Solution: -

HTML Code:

<!DOCTYPE html>
<html>
<head>
<meta charset=utf-8/>
<title>A passed string is palindrome or notlt;/title>
</head>
<body>
  
</body>
</html>

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('nurses run');
check_Palindrome('fox');

Sample Output:

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

Flowchart:

Flowchart: JavaScript function: Check whether a passed string is palindrome or not

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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JavaScript: Tips of the Day

How to check whether a string contains a substring in JavaScript?

ECMAScript 6 introduced String.prototype.includes:

const string = "foo";
const substring = "oo";

console.log(string.includes(substring));

includes doesn't have Internet Explorer support, though. In ECMAScript 5 or older environments, use String.prototype.indexOf, which returns -1 when a substring cannot be found: 

var string = "foo";
var substring = "oo";

console.log(string.indexOf(substring) !== -1);

Ref: https://bit.ly/3fFFgZv