Arguments casting to array.

[EvanCarroll]

The current advice,

To convert an array-like object to an array, use Array#slice.

function trigger() {
  var args = Array.prototype.slice.call(arguments);
  ...
}

Actually breaks v8's compiling optimizer, just fyi. Any function you do that to can not be optimized. See the bluebird docs for more info.

Also, see my question on StackOverflow.

[goatslacker]

In this particular case we're favoring readability > performance.

Directly assigning to an Array with a fixed length (like it mentions in the bluebird docs for "Workaround") is way faster anyway but that doesn't mean we should always favor that pattern.

[EvanCarroll]

Well, just so long as you're comfortable totally forgoing javascript optimizations everywhere that pattern is used. Afaik, no browser can or will ever optimize if you leak arguments. For this reason, I find this to be bad advice. You're taking a shortcoming of the language (the arguments object), and advocating exactly the reason why arguments is a shortcoming.

It's not just the act of the copying to an array either. It's the entire containing function. The whole thing is marked un-optimizable.

[goatslacker]

Thankfully we've got rest in es6 so we don't have to ever use arguments :)

[ljharb]

Since now we should be using the rest operator, I'm going to close this.