我怎样才能在javascript中使用return

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

var result = add(3, 4);
console.log(result); // 输出7

function createPerson(name, age) {
  return {
    name: name,
    age: age
  };
}

var person = createPerson("John", 25);
console.log(person.name); // 输出John
console.log(person.age); // 输出25

function createGreeter(greeting) {
  return function(name) {
    console.log(greeting + ", " + name + "!");
  };
}

var greet = createGreeter("Hello");
greet("John"); // 输出Hello, John!