All iterables have a special structure called iterator. An iterator is a function that allows you to iterate over an object.
Let's look at an array example:
let arr = [1, 2, 3];
The iterator function for any iterable
object is stored with a key in the form
of the well-known symbol Symbol.iterator
:
let func = arr[Symbol.iterator];
We can make sure that the function is stored under this key (but its code will be hidden from us by the browser):
console.log(func); // the function
Check the different types of iterables you know to see if they contain the described function.