Accessing arguments collection in bind function

Question

When returning .bind() from a higher order function, is it possible to access the arguments collection within the bound context?

Take the following function as an example:

function reverse(fn) {
     return function ()  { 
        return fn.apply(this, [].slice.call(arguments).reverse()) 
     };
}

Ideally I'd like to remove the inner function wrapper and simply return something like:

return fn.apply.bind(fn, [].slice.call(arguments).reverse());

(Obviously arguments is scoped to the outer function and not the returned function, which is what I'm after).

Is this possible through some mechanism I'm unaware of or is the function wrapper a necessity?

I can't figure out what you're actually trying to achieve... — Alnitak
– Alnitak, Commented Jan 20, 2015 at 15:22
The removal of the inner function (return function () {...}) — Jamie Dixon
– Jamie Dixon, Commented Jan 20, 2015 at 15:23
The outer function takes a function, and returns a function that is the same as the one passed in, except the arguments are reversed. So reverse(console.log)("World", "Hello") -> "Hello" "World" — Jamie Dixon
– Jamie Dixon, Commented Jan 20, 2015 at 15:25

Alnitak · Accepted Answer · 2015-01-20 19:42:33Z

1

.bind is a good way of setting the context and/or a fixed initial parameter list when you cannot control the lexical scope of the function you're trying to .bind.

Internally .bind just creates a function anyway, so offers no advantage here - in my experience it has few other uses that an inner function wouldn't achieve better.

In fact in this case it simply can't work - you have to provide some sort of scope for where the .reverse() call happens, and the only place that can be is in that inner function.

edited Jan 20, 2015 at 19:42

answered Jan 20, 2015 at 15:28

Alnitak

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3 Comments

Jamie Dixon Over a year ago

This is just for practice but it would have been more aesthetically pleasing to my pedantic mind if I could have removed the inner function got away with a one liner. Ah well. Onward and up. Cheers for answering Alnitak.

nullpotent Over a year ago

If it's just for the aesthetics of a one liner, you could do this: return Function(["fn"], "fn.apply(fn, [].slice.call(arguments, 1).reverse());").bind(null, fn); but that's just awful for my taste.

Alnitak Over a year ago

@JamieDixon ultimately, you have to arrange for the argument array to be reversed before invoking the desired function, and AFAIK that's simply impossible with a call to .bind. You have to provide some scope in which that reversal takes place, and your inner function provides that.

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