countup.js

function countup (n) {
  console.log(`we are in ${arguments.callee.name}(${n})`);
  console.log(`is ${n} < 1?`, n < 1);
  
  if (n < 1) {
    console.log(`so we're going to return [] back to the caller\n↓`);
    return [];
  }

  console.log(`so we call countup(${n-1})\n↓`);
  const countArray = countup(n-1);

  console.log(`we are back in ${arguments.callee.name}(${n})`);
  console.log(`now we push ${n} into countArray, which is currently [${countArray}]\n↓`);
  countArray.push(n);
  return countArray;
}

console.log(countup(5));