optional typing.js

// optional typing for function parameters
// Allows you to use a string literal in front of the variable name
// This string literal must be a valid [[Class]] value
// And the function when invoked should throw a type error if the argument passed // in doesn't have the correct [[Class]] value
// If an argument is not passed in, the function should not throw an error

function Func("Function" f, "Array" arr) {
  return f(arr);
}

// Works
Func();
Func(function () { });
Func(function () { }, []);

// Fails
Func([]);
Func("foo");