None.

The same return value as Array.prototype.values(): a new iterable iterator object that yields the value of each index in the arguments object.

Note that you seldom need to call this method directly. The existence of the @@iterator method makes arguments objects iterable, and iterating syntaxes like the for...of loop automatically call this method to obtain the iterator to loop over.

function f() {
  for (const letter of arguments) {
    console.log(letter);
  }
}
f("w", "y", "k", "o", "p");

You may still manually call the next() method of the returned iterator object to achieve maximum control over the iteration process.

function f() {
  const argsIter = arguments[Symbol.iterator]();
  console.log(argsIter.next().value); // a
  console.log(argsIter.next().value); // b
  console.log(argsIter.next().value); // c
  console.log(argsIter.next().value); // d
  console.log(argsIter.next().value); // e
}
f("w", "y", "k", "o", "p");

• Functions guide
• Functions
• arguments
• Array.prototype.values()
• Symbol.iterator
• Iteration protocols