I dislike that syntax, but it might be better to instead use a special syntax that can't be the name of any variable, like the asterisk in Raku as mentioned below. In such a case, perhaps the function that would call it should check if the value is already the correct type and use that instead of calling it as a function, since then it would be possible for the filter condition to be a constant true or false that does not depend on the values being filtered (this is not usually useful, but it is more consistent and sometimes it is useful).

I think that the automatic semicolon insertion is a bad feature of JavaScript.