// 1. One parameter in ES6
let sum = (a, b) => a + b;

  // in ES5
  var sum = function(a, b) {
    return a + b;
  };

// 2. Without parameters in ES6
let randomNum = () => Math.random();

  // in ES5
  var randomNum = function() {
    return Math.random();
  };

// 3. Without return in ES6
let message = (name) => alert("Hi " + name + "!");

  // in ES5
  var message = function(yourName) {
    alert("Hi " + yourName + "!");
  };