Memoize a function

JavaScript version
const memoize = (fn) =>
(
(cache = Object.create(null)) =>
(arg) =>
cache[arg] || (cache[arg] = fn(arg))
)();
Examples
// Calculate Fibonacci numbers
const fibo = memoize((n) => (n <= 2 ? 1 : fibo(n - 1) + fibo(n - 2)));
fibo(1); // 1
fibo(2); // 1
fibo(3); // 2
fibo(4); // 3
fibo(5); // 5
fibo(6); // 8