计算一个回文串中有多少个回文子串

const palindrome = function (str) {
  if (typeof str !== 'string') {
    return false;
  }
  if (str.split('').reverse().join('') === str) {
    return true;
  } else {
    return false;
  }
}

const palindromeCount = function (str) {
  const len = str.length;
  let count = 0;
  for (let i=0; i<len-1; i++) {
    for (let j=i+1; j<len; j++) {
      if (palindrome(str.slice(i,j+1))) {
        count++;
      }
    }
  }
  return count;
}

console.log(palindromeCount('abc')); // 0
console.log(palindromeCount('abba')); // 2
console.log(palindromeCount('abbabba')); // 7