check if a string is a palindrome

palindrome.js

// Input: str
// Output: true or false

// Example: madam -> 5 length, odd
// Example: wowwow -> 6 length, even
// Example: hello -> fail, odd
// Example: hi -> fail, even

// isPalindrome(str)
  // midpoint str/2 ceil -1
  // for loop until <= midpoint
    // up = str[i]
    // down str[length -1 -i]
    // if not equal, return false
  // return true

function isPalindrome(str) {
  if (str === 0 || str.length === 1) {
    return true;
  }
  
  for (let i = 0; i <= mid; i++) {
    let up = str[i];
    let down = str[str.length - 1 - i];
    if (up !== down) {
        return false;
    }
  }
  
  return true;
}