nodejs `arguments` is object but in the browser, it is an `array`

When I access arguments from inside called function in nodejs...

echo '!function(){ console.log(arguments) }(1,2,3)' | node

... it outputs an object ...

{ '0': 1, '1': 2, '2': 3 }

... but in google chrome ...

!function(){ console.log(arguments) }(1,2,3)

... outputs ...

[1, 2, 3]

Why is it not consistent? What other js environments have this different behaviour? Is it ok for me to use arguments? How can I ensure it is always an array before I use it?