// Flip every pair of characters in a string.


// Example:
// var input = 'check out how interesting this problem is, it\'s insanely interesting!';
// var output = flipPairs(input);
// console.log(output); // --> hcce kuo toh wnietertsni ghtsip orlbmei ,si 't sniasenyli tnreseitgn!
// input = string
// output = string

function flipPairs(string) {
  var flipArray = [];
  //Iterate over the characters of the string increment : 2
  for (var i = 1; i < string.length; i += 2) {
      flipArray.push(string[i]);
      flipArray.push(string[i - 1]);
  }
  if (string.length % 2 === 1) {
    flipArray.push(string[string.length-1]);
  }
  return flipArray.join('');
}

var input = 'check out how interesting this problem is, it\'s insanely interesting!';
var output = flipPairs(input);
console.log(output);

function assertEqual(actual, expected, testName) {
  if (actual === expected) {
    console.log('passed');
  } else {
    console.log('FAILED [' + testName + ']');
  }
}

console.log(assertEqual(output, "hcce kuo toh wnietertsni ghtsip orlbmei ,si 't sniasenyli tnreseitgn!", 'String Equality'));