Why not? lol

Nicely but slowly. In most cases we don't need to use this generic solution for every type.

Hi, I think, that Kata's example is not properly and can discourage. Below is example, that Kata offered to repeat:
logOnce = once(console.log)
logOnce("foo") // -> "foo"
logOnce("bar") // -> no effect

But it's not possible and no one of best solutions can do it (check it yourself). Why? Because "console.log" has their own "this" and in addition to "logOnce = once(console.log)" you must bind console's object like this:
logOnce = once(console.log).bind(console);

In this case function will be work fine. Please, fix example case or provide another one, because existing is mismatched

Guys, read the description, please: "calculateHypotenuse(3,4); // returns 5". Your function will return "5.000"