Passing return value as function arguments (tuple)

Question

I'm trying to use the return value of my function as arguments for my function, however the fact that it's a tuple is being problematic. This is further compounded by the fact that it will not always be a tuple.

function foo(initial_state, indexer = 0) {
// does something

return [initial_state, indexer + 1];
}

I want to be able to sometimes use the function as simply

foo(initial_state);

but also I want to call the function with the return, as such..

foo(foo());

Instead of the desired behavior, the tuple is put into initial_state, whereas I would want it deconstructed to match the arguments in the function.

I can obviously do a temporary variable like

let some_state, some_index = foo();
foo(some_state, some_index);

But that seems very ugly. There has to be a better way.

Answer 1

Use the spread syntax:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_syntax

function foo(initial_state, indexer = 0) {
  return [initial_state, indexer + 1];
}

console.log(foo(...foo(0, 0)));