What I've done today is Find the divisors! in JavaScript.

CodeWars

Problem

Find the divisors!

Create a function named divisors/Divisors that takes an integer n > 1 and returns an array with all of the integer's divisors(except for 1 and the number itself), from smallest to largest. If the number is prime return the string '(integer) is prime' (null in C#) (use Either String a in Haskell and Result<Vec<u32>, String> in Rust).

Example:

divisors(12); // should return [2,3,4,6]
divisors(25); // should return [5]
divisors(13); // should return "13 is prime"

Solution

function divisors(integer) {
  s = Array.apply(null, {length: Math.ceil((integer+1)/2)}).map(Number.call, Number).slice(2).filter(x => integer % x===0);
  return s.length?s:`${integer} is prime`;
};