How to write palindrome in JavaScript

Question

I wonder how to write palindrome in javascript, where I input different words and program shows if word is palindrome or not. For example word noon is palindrome, while bad

Answer 1

Note: This is case sensitive

function palindrome(word)
{
    for(var i=0;i<word.length/2;i++)
        if(word.charAt(i)!=word.charAt(word.length-(i+1)))
            return word+" is Not a Palindrome";
    return word+" is Palindrome";
}

Here is the fiddle: http://jsfiddle.net/eJx4v/

Answer 2

Try this

isPalindrome = (string) => {
    if (string === string.split('').reverse().join('')) {
        console.log('is palindrome');
    }
    else {
        console.log('is not palindrome');
    }
}

isPalindrome(string)

Answer 3

You could also do something like this :

function isPalindrome(str) {
var newStr = '';

for(var i = str.length - 1; i >=0; i--) {
    newStr += str[i];
}

if(newStr == str) {
    return true;
    return newStr;
} else {
    return false;
    return newStr;
}
}

Answer 4

Frist I valid this word with converting lowercase and removing whitespace and then compare with reverse word within parameter word.

function isPalindrome(input) {
    const toValid = input.trim("").toLowerCase();
    const reverseWord = toValid.split("").reverse().join("");
    return reverseWord == input.toLowerCase().trim() ? true : false;
}
isPalindrome("    madam ");
//true

Answer 5

25x faster + recursive + non-branching + terse

function isPalindrome(s,i) {
 return (i=i||0)<0||i>=s.length>>1||s[i]==s[s.length-1-i]&&isPalindrome(s,++i);
}

See my complete explanation here.

Answer 6

    function palindrome(str) {
        var re = /[^A-Za-z0-9]/g;
        str = str.toLowerCase().replace(re, '');
        var len = str.length;
        for (var i = 0; i < len/2; i++) {
            if (str[i] !== str[len - 1 - i]) {
                return false;
            }
        }
        return true;
    }