Palindrome and Fibonacci

js_exercises.js

function IsPalindrome(some_txt) {
  var text_length = some_txt.length;
  var success, j = text_length - 1;
  var mid = Math.floor(text_length / 2);

  for(var i=0, il=text_length-1; i < il; i++) {
    if(some_txt[i] !== some_txt[j]) {
      success = false;
      break;
    } else {
      j--;
    }
    success = true;
  }

  return success;
}

function Fibonacci(n) {
  var _sums = {};

  var calculateFib = function(n) {
    if(n === 0) return 0;
    if(n === 1) return 1;
    if(_sums[n]) { return _sums[n]; }

    _sums[n] = calculateFib(n-1) + calculateFib(n-2);
    return _sums[n];
  };

  calculateFib(n);
}