ispalindromewithouttests.js

// checks two moving indices and stops when needed
const isPalindrome = (arr) => {
  // symmetry will always be found in one or 0 elements
  // [1] -> true
  // [] -> true
  if (arr.length < 2) return true;
  // taking two pointer approach
  let first = 0;
  let last = arr.length - 1;
  while (first < last) {
      // if symmetry is broken, stop RIGHT there
      if (arr[first] !== arr[last]) return false;
      // walk our pointers
      first += 1;
      last -= 1;
  }
  // if symmetry is unbroken throughout string
  // string is symmetrical
  return true;
};