BonsaiDen
commented
13 years ago The arguments Object
The spec never says that it can be omitted, also, I did some testing in recent browsers there was no speed difference at all between functions that used arguments and function that don't.
The Array.prototype.slice.call is there to show how to convert it to an array, foo.apply(some, arguments) can't be used all the time, of course it would be good to note there just in case people still don't get it after reading the rest of the guide.
"but still this should avoided as often as possible" there is no performance penalty whatsoever.
ES5 errata
Good catch, I'll add that as a ES5 note, IE in quirks still returns object for both undefined and null though.
undefined
Yes, should be changed to "some examples"
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evilpie
jdalton
Just noticed that this is hosted on github, after sending an email, dooh. Here is the copy:
The arguments Object "The arguments is, except for the two cases named at the start of this section, always created." Not really true, if it's not used in any function having access to this scope it's not created in the most cases and engines. "Array.prototype.slice.call" Please don't show this code, somebody will copy it, make some benchmarks. Array.apply(null, arguments); should be at least twice as fast usually, but still this should avoided as often as possible.
The class of an object Just wanted to note that a ES5 errata changed Object.prototype.toString, so toString.call(null) returns [object Null] and undefined [object Undefined] In general, there is no need use the strict equality operator with typeof, but that's more an personal preference.
undefined and null "But this variable is not a constant, meaning that it can be easily overwritten which then leads to abstruse bugs" undefined is not writable in ES 5, but still not an keyword (so it could be shadowed) "The value undefined is returned in the following cases:" The list is not conclusive (eg void 0, [].shift()), i would change to "some example to get the undefined value"