The arguments
object is available within any JavaScript function. It is
an array-like object with all of the arguments to the function. Even if not
all of the arguments are referenced in the function signature, they can
still be accessed via the arguments
object.
function argTest(one) {
console.log(one);
console.log(arguments);
console.log(arguments[1]);
}
argTest(1);
// 1
// [1]
// undefined
argTest(1, 'two', true);
// 1
// [1,'two',true]
// 'two'
See the Arguments object docs on MDN for more details.
h/t Dorian Karter