function sum(a, b) {
  return a + b;
}

let sumArrow = (a, b) => {
  return a + b;
}

let sumArrowShort = (a, b) => a + b;


function isPositive(n) {
  return n > 0;
}

let isPositiveArrow = (n) => {
  return n > 0;
}

let isPositiveArrowShort = (n) => n > 0;


function randomNumber() {
  return math.random;
}

let randomNumberArrow = () => {
  return math.random;
}

let randomNumberArrowShort = () => math.random;


document.addEventListener('click', function() {
  console.log('Clicked.');
});

document.addEventListener('click', () => {
  console.log('Clicked.');
});

document.addEventListener('click', () => console.log('Clicked.') );