Neat, but I think that functions already do what we need.

For one thing, the example isn't the most compelling, because you can:

    const greeting = 'hello'.toUpperCase() + '!!!';

or

    const greeting = 'HELLO!!!';

That said, there is already:

    function thrush(initial, ...funcs) {
        return funcs.reduce(
            (current, func) => func(current),
            initial);
    }

    const greeting = thrush('hello', s => s.toUpperCase(), s => s + '!!!');