Any discussion of "compact" subset for mobile devices?

Brendan Eich brendan at
Thu Mar 20 23:15:00 PDT 2008

On Mar 20, 2008, at 10:56 PM, ToolmakerSteve98 wrote:

> After a rough look at the size of the language grammar and spec, and
> perusing some of the past mail discussions about subtleties in
> parsing/analyzing certain constructs -- WHOA - this is stuff we  
> take for
> granted on our multi-GHz and GB desktop PCs today,

I think you need evidence to justify your gut ("WHOA") reaction. I'll  
be first to admit we need evidence to prove the incremental cost of  
ES4 over ES3 is not excessive, but participants in Ecma TC39 who  
believe this can be done are targeting mobile devices and working on  
real, small footprint implementations right now (e.g. ESC plus  
Tamarin Tracing). Anyway, whatever the jump in JS evolution (ES3.1,  
ES4), IMHO there's no "third" way that forces a static language and  
offline/AOT compilation.

> but ES4 would
> web-standardize a language that would require every web client to  
> take on
> that burden.

Browsers have to handle today's JS plus several other content  
languages and image formats, with video and audio coming. Life in the  
big city. The CPU budget should not go up significantly due to ES4  
features, and compiled and burned-into-ROM code footprint may shrink  
if we make the right self-hosting trades. But we have to prove this,  
as noted above.

> My gut reaction is that Microsoft has taken a better tack: let
> this stuff be resolved at authoring time down to a CLR. Don't  
> burden every
> web client device with it.

That's not the web, sorry. JavaScript is and will remain a web source  
language for the foreseeable future. The Ecma TG1 (now TC39) group  
charged with maintaining and improving its standard is not going to  
throw it out and require a CLR-like VM and standardized interchange  
bytecode. Nor are web developers going to switch horses (really, ride  
both old and new horses) like that in significant numbers, from what  
I can see.

> That's why I ask about "compact" subset. I'm initially skeptical  
> that what
> I'm seeing is the right next step for the web.

You may not have heard from many people (see my blog for some  
comments from them) who think a statically typed language that must  
be compiled ahead of time is the wrong thing for the web. Opinions  
vary, but it's clear there is no practical way to move web browsers  
and content en masse to such a model in anything like the timeframe  
contemplated for ES4. Such a move seems obviously a much bigger  
effort than the ES4 effort.

> But I think there are a lot
> of good ideas here, so I'm working through it, looking for common  
> ground
> between stuff I see at Microsoft and stuff I see here.

Why do you believe static typing is necessary for performance? Just  

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