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:

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:

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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Previous: Write a JavaScript function that reverse a number.
Next: Write a JavaScript function that generates all combinations of a string.
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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
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