substring-palindrome.js

/***
Given a string X, will return true if palindrome and false if not
Return value: bool
***/
const isPalindrome = (string) => {
  return string === string.split("").reverse().join("")
}

/***
Given a string X, will return longest substring that is a palindrome, if it exists.
Return value: string
***/
const pSubstring = (string) => {
  // Is this thing already a palindrome? Then return it and call it a day.
  if (isPalindrome(string)){
    return string
  }
  // Ok, it's not, so let's dig.
  const possibilities = []

  for (let l = string.length - 1; l > 0; l--){
    string = string.slice(0, l);
    for (let i = 0; i < string.length; i++){
      let subString = string.slice(i);
      if (subString.length > 2 && isPalindrome(subString)){
        possibilities.push(subString)
      }
    }
  } 
  
  // No matches? bail
  if (possibilities.length === 0){
    return "You got nothing";
  }

  // Return longest match
  return possibilities.reduce((acc, string) => acc.length < string.length ? string : acc, possibilities[0]);
}

pSubstring("hellobablo") // "bab"