Functions can be defined inside other functions:

const test = function() {
  const dosomething = function() {
    /* do something */
  }
  dosomething()

  return "test"
}

Arrow functions can contain other arrow functions, or regular functions too. You can mix them:

const test = () => {
  const dosomething = () => {}
  dosomething()
  return "test"
}

The nested function cannot be called from outside the enclosing function, only from inside it.

Lessons in this unit:

0:	Introduction
1:	Function parameters
2:	Returning values from a function
3:	Arrow functions
4:	▶︎ Nesting functions
5:	Immediately-invoked functions
6:	Recursive functions