Palindrome

index.js

function compare(s, i, p, n) {
  const current = s[i]
  const prev = i > 0 ? s[i - p] : ''
  const next = i < (s.length - n) ? s[i + n] : ''

  if(s.length == 1)
    return false

  if(prev == next)
    return [p+1, n+1, true]
    // return compare(s, i, p+1, n+1)
  
  if(n == 1 && prev == current)
    return [p+1, n, true]
    // return compare(s, i, p+1, n)
  
  return [p, n, false]
}

var longestPalindrome = function(s) {
  let index = 0, 
  longest = 1,
  p = 1, 
  n = 1

  for (let i = 0; i < s.length; i++) {
    let v = [1,1]
    while (true) {
      v = compare(s, i, v[0], v[1])
      if ((v[0] + v[1]) > longest) {
        index = i
        longest = (v[0] + v[1])
        p = v[0]
        n = v[1]
      }

      if(!v[2]) break
    }
    

  }

  const pali = s.substr(index - (p - 1), p + n - 1)
  return pali
};