Spread element magically turns functions into 'not functions'

Question

Suppose I have this simple JavaScript function:

function returnArray(){
    return [1, 2, 3];
}

Further suppose that I then say

<         


        

Answer 1

Just a minor change:

function double(array) {
  // note the return here is an array, not a number
  if (array.length === 1) return [2 * array[0]];

  var [num, ...rest] = array;
  if (rest.length) return [2 * num, ...double(rest)];
}

console.log(double([1, 2, 3, 4]));

You were returning a number, and destructuring a number will leave you with an error.

...5 // throws SyntaxError