1)
function calculate(a, b) {
  var sum = a + b;
  var difference = a - b;
  var product = a * b;
  var quotient = a / b;

  return [sum, difference, product, quotient];
}
2)function calculateSquare(a) {
  var perimeter = 4 * a;
  var area = a * a;

  return [perimeter, area];
}