map_hoc.js

function number2String(number) {
  return number.toString(10);
}

function myMap(numbers, fn) {
  const elements = [];

  for(let i = 0; i < numbers.length; i++) {
    elements.push(fn(numbers[i]));
  }

  return elements;
}

const strings = myMap([1, 2, 3, 4], number2String);
console.log(strings);