Sure, once it's in the language spec and doesn't use Array hacks.

jacobolus · on Nov 16, 2009

What’s an “array hack”? Using Array.prototype.slice on the arguments object? You’re going to have to provide some evidence that language designers didn’t intend that to be possible, before you criticize it. It works perfectly well in every JavaScript implementation. From my perspective, it’s quite often the only reasonable way to deal with the arguments object, and one of the most powerful and flexible ways of making functions with useful APIs in JavaScript.

bumblebird · on Nov 16, 2009

Turning an object into an array isn't a nice way to do things IMHO. Maybe runtimes optimize for these cases, or maybe they create completely new objects every time and you get fantastic object churn.

Yes it works well, but it's not really necessary. It's inefficient wasted effort.

I guess it's fun to make lovely APIs, but that doesn't help people who just want their js to run fast.

jacobolus · on Nov 16, 2009

> Turning an object into an array isn't a nice way to do things

This doesn’t happen. The object is unchanged when you call array.slice.

> Maybe runtimes optimize

Only insofar as the built-in array methods are optimized anyway.

> maybe they create completely new objects

No, they don’t. Or rather, yes, array.slice creates a new object to put the slice in, but only because that is part of its declared API.

> Yes it works well, but it's not really necessary.

What’s the alternative?

> It's inefficient wasted effort.

Inefficient how? If you time it, it’s faster other ways of accomplishing the same thing. Whose wasted effort? It certainly saves me time as a JavaScript developer.

* * *

To be honest, I think that arguments should just be an array (then we wouldn’t have any of this trouble), but I assume that’s not possible for the language at this point.

bumblebird · on Nov 16, 2009

>> This doesn’t happen. The object is unchanged when you call array.slice.

You're wrong. Why don't you check instead of reading API docs or saying what you think should happen? It obviously is changed, and is a new object: Array.prototype.slice.call({0:"hello",1:"world",foo:"bar",length:2});

Results in ["hello","world"] - the result is a completely new object - inefficient wasted effort. Both in cpu and memory.

Offtopic again, but here's an interesting way to make a new N element array, initialized with undefineds...

Array.prototype.slice.call({length:100}) = [undefined, undefined, undefined........ undefined]

Array.prototype.slice.call({length:10000000}) takes almost 1 second to run on my MBP while it's creating that new array.

>> What’s the alternative?

As I say, just write closures...

onclick = function(c){return function(){c.doSomething()}}(this);

It's not much more typing, and is more general. I agree arguments would be nicer if it was a true array though.

bumblebird · on Nov 16, 2009

Instead of downmodding, why not explain why you disagree with the facts I present above?