In like 99% of all the cases, it's not. Only every few months I find a problem that is slow and refactoring it to something other than `map` shows a discernible improvement.
So it's rare.
Well, it crashes the tool but passes all the requirements:
(function(){
var fn = Math.random() <= 1 ? "Date": "";
console.log(window[fn].now());
})();
Output:
TODO
__IntrospectionError
at repl:3:22
at repl:1:1