Catchall invocation for 'null' and 'undefined' (or: how to be a disruptive influence in 3 easy steps)

[Brendan Eich]

Shaver raised the general point that Object types cannot convert to  
any boolean value other than true, per ES1. I've mentioned before that  
this was not what Netscape's JS implementation did, but in order to  
avoid multiple implicit conversions to boolean due to chained && and  
||, we agreed to make ToBoolean(obj) = true for all Object-typed (ES1  
term: any non-primitive) obj.

We'd have to revisit this, at least.

My sense is that most people don't feel strongly enough to put in the  
work to develop this Smalltalk nil idea so that it is both complete  
and compatible. The Java-ish null (really, C-ish) design decision is  
hard to revoke. Catchalls are not enough to change null and undefined  
to be of Object type (again that pesky ES spec language).

I regret not making *everything* an object, FWIW. "Make it look like  
Java" + lazy/fast machine types for numbers + zero time to implement  
in May 1995.

/be

On May 15, 2009, at 10:45 AM, William Edney wrote:

> All -
>
> I sent this about 1.5 weeks ago, but have gotten no responses. I can  
> attribute this to 2 possible items:
>
> 1. I made the mistake of replying to an existing message so this one  
> got buried under a thread it shouldn't have.
>
> 2. Folks were so horrified as to what I was asking for that they  
> really just wished I would go away :-).
>
> I'll repeat the message here. If the answer is #2, please let me  
> know and I'll crawl back under my rock :-).
>
> Cheers,
>
> - Bill
>
>
>
> All -
>
> Well, Sister Eugenia always did say I was a disruptive influence in  
> grade school - guess I haven't changed much :-).
>
> Let me throw another idea into the mix and churn the pot a bit more.
>
> Many moons ago when I was a Smalltalker, I always liked the fact  
> that 'nil' in Smalltalk was a singleton instance of  
> UndefinedObject... and you could add methods to UndefinedObject :-).
>
> Like... doesNotUnderstand.
>
> When I switched to JS, I found out that 'null' and 'undefined' were  
> 'special' and weren't instances of anything I could add methods to  
> (cue wailing and gnashing of teeth).
>
> I always thought it would be most interesting if the following were  
> true: 'null' was the singleton instance of the Null type and  
> 'undefined' was the singleton instance of the Undefined type.
>
> Then, I could do the following (which would have saved me a lot of  
> debugging time over the years):
>
> (Using the older __noSuchMethod__ syntax):
>
> Null.prototype.__noSuchMethod__ = function (id, args)
> {
> alert('you were a bad boy and tried to send ' + id + ' to null');
> }
>
> Undefined.prototype.__noSuchMethod__ = function (id, args)
> {
> alert('you were a bad boy and tried to send ' + id + ' to undefined');
> }
>
> My business partner Scott has bugged Brendan about this in the past  
> and he mentioned that ES3 was too set in its ways to do anything  
> like this, but I figured maybe with Harmony on the horizon, the  
> issue could be revisited :-). I have no idea regarding the  
> implications of such a change and therefore leave it to you all to  
> consider those implications.
>
> Thoughts?
>
> Cheers,
>
> - Bill
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