- From: Boris Zbarsky <bzbarsky@MIT.EDU>
- Date: Thu, 10 Feb 2011 22:51:18 -0500
On 2/10/11 10:32 PM, timeless wrote:
> i believe the only requirements for:
>
> <script>
> function x(){....}
> function y(){....}
> </script>
>
> are:
> 1. if x fails to compile, y is not evaluated
> 2. y can fail to compile too
> 3. if something fails to compile, window.onerror is triggered
> 4. if x could compile, then window.x is defined to be a Function object
I don't think so. If there is any parse or compilation or whatever you
want to call it error, the script is never executed, so window.x is
never defined.
Also, I would fully expect it to be a web compat requirement that
window.onerror not be triggered until the script would be evaluated. If
you parse/compile/whatever before that and hit an error, you'd need to
save that and report it at the "right" time.
Which means the that parse/compile/whatever process is currently not
observable directly. And that's a good thing!
> in theory, i believe a js engine could choose to discard all work it
> has done to validate syntax for x+y beyond saving those coordinates,
> and then either do the proper ast / bytecode / machine code generation
> lazily (or schedule to do it on a thread).
Sure; a js engine could also not do any syntax validation at all, until
it needs to run the script...
-Boris
Received on Thursday, 10 February 2011 19:51:18 UTC