How to check if a string is a palindrome JavaScript [CLOSED!]

Question

I'm trying to make a function that will check if a word is a palindrome. If the word is a palindrome it will return true else it will return false. "You'll need to remove all non-alphanumeric characters (punctuation, spaces and symbols) and turn everything lower case in order to check for palindromes.

We'll pass strings with varying formats, such as "racecar", "RaceCar", and "race CAR" among others."

My code is:

function palindrome(str) {
  str = str.toLowerCase().replace(/[^a-z]+/g,"");
  if (str === str.split("").reverse().join("")){
    return str;
  } else {
  return "This is not a palindrome";
  }
}

Could somebody tell me what is wrong with this code please?

check this: http://stackoverflow.com/questions/233243/how-to-check-that-a-string-is-a-palindrome-using-regular-expressions — John, Apr 08 '16 at 20:42
In what way isn't it working? It looks like it works to me, except you probably need to return `true` and `false` instead of `str` and `"This is not a palindrome"` — Robert Hickman, Apr 08 '16 at 20:43
http://stackoverflow.com/questions/22349358/finding-palindrome-using-regex — John, Apr 08 '16 at 20:46
It doesn't work because it always return a "true" because if not palindrome, then return a string, which evaluated as a boolean is **true**. — Fabricio, Apr 08 '16 at 20:47
The function returns true regardless of whether the phrase or word is or isn't a palindrome: e.g 'palindrome("1 eye for of 1 eye");' still returns true — Marc Freeman, Apr 08 '16 at 20:47
Because you stripped out the numbers. See my previous comment. — j08691, Apr 08 '16 at 20:51

score 2 · Accepted Answer · answered Apr 08 '16 at 20:48

2

How about this solution.

function palindrome(str) {
  str = str.toLowerCase().replace(/[^a-z0-9]+/g,"");
  return str === str.split("").reverse().join("");
}

It strips non alpha-numeric characters, turns into lower case, and returns true | false

answered Apr 08 '16 at 20:48

Unamata Sanatarai

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Thank you! Could you explain why this works without the boolean logic? It's got me a bit stumped as the problem statement required me to return a "true" or "false" value depending on whether the word was a palindrome or not. – Marc Freeman Apr 08 '16 at 20:53
a comparison, i.e. `===` (or `==`) returns true or false. So the function compares parsed-input-string, with its reverse. If both are equal, it returns `true` – Unamata Sanatarai Apr 08 '16 at 20:55
Of course! I always forget that the equality and strict equality comparators compare two pieces of code and give a true or false statement in return. – Marc Freeman Apr 08 '16 at 21:09

score 1 · Answer 2 · answered Apr 08 '16 at 20:48

"alphanumeric" means both alphabetical and numerical characters. Try something like this:

function isPalindrome(str) {
  str = str.toLowerCase().replace(/[^a-z0-9]+/g, '');

  return str === str.split('').reverse().join('');
}

isPalindrome('racecar')
// => true

isPalindrome('race car')
// => true

isPalindrome('race caR')
// => true

score 0 · Answer 3 · answered Apr 08 '16 at 20:47

0

It doesn't work because it always return a "true" because if not palindrome, then return a string, which evaluated as a boolean is true.

answered Apr 08 '16 at 20:47

Fabricio

3,248
2
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How to check if a string is a palindrome JavaScript [CLOSED!]

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