What does this code mean?

[html08]

Continuing the discussion from freeCodeCamp Challenge Guide: Arguments Optional:

I don’t fully understand the logic of this solution. What does it mean when you put const [something here]. I understand that it sets first and second to the arguments object inputs but why is the [ ] needed? Does it create an array?

Also, I don’t fully understand how the second argument is accessed if it is not included in the original parameters of the function. For example, addTogether(2)([3]). How is the [3] accessed by arguments if it’s not an argument in the original call addTogether(2)?

CamperBot Solution:

@camperbot

function addTogether() {
  const [first, second] = arguments;
  if (typeof(first) !== "number")
    return undefined;
  if (arguments.length === 1)
    return (second) => addTogether(first, second);
  if (typeof(second) !== "number")
    return undefined;
  return first + second;
}

[JeremyLT]

That syntax is called destructuring.