The challenge, should you choose to accept it, is to recreate this (or a similar API) yourself. If you're anything like me, you'll learn a bunch!
// Using the calculator! calculator.one.plus.two.plus.three.equals => 6 calculator.two.plus.four.plus.seven.plus.eight.equals => 21
Hint: The solution is not to just use a single object with heaps of very deeply nested properties 😛