[Laszlo-dev] Javascript optimization hints [Was: [Laszlo-checkins] r5888 - in openlaszlo/branches/wafflecone: WEB-INF/lps/lfc/data WEB-INF/lps/lfc/events WEB-INF/lps/lfc/views lps/components/base]

[Max Carlson]

Thanks for the tips - it's always good to have a reminder :).

Just so I'm clear, we can now use JS2 type declarations:

var uplinkArray: Array;

but they'll be ignored (for now).  Is this correct?

If so, it'll be a good task for someone to go through the LFC and add 
type annotations sooner rather than later!

P T Withington wrote:
> Since the compiler does not do common-subexpression elimination, when 
> you are trying to optimize things, pretend you are writing in 1985 C.  
> Instead of:
> 
>   if (d.c[d.f]) d.c[d.f]( sd )
> 
> say:
> 
>   var f = d.c[d.f];
>   if (f) f(sd);
> 
> Even better, when you find yourself having to write a null check, ask 
> yourself if it would be cleaner, simpler, and more efficient to have the 
> variable you are referencing not be nullable.  For instance, if a 
> variable is an array, consider using an empty array for its initial 
> value, rather than null.  This is a time/space trade-off:  if there are 
> many operations on the array and the variable is almost always not null, 
> it will be more efficient to use an empty array; if there are few 
> operations and the variable is usually null, then not allocating the 
> empty array is the better choice.
> 
> (In Javascript 2, you will have the option of declaring a variable to be 
> of a particular type, and you will have the option of declaring wether 
> or not that variable can also be null.  If you declare it not to be 
> nullable, then the compiler will give you a compile-time warning if it 
> cannot prove that the variable is never null, and it will insert the 
> appropriate runtime check for you.
> 
>   // This can be null, you have to check before using
>   var uplinkArray: Array;
> 
>   // This cannot be null, you have to give a valid initial value
>   var uplinkArray: Array! = new Array();
> 
> Even though we don't yet support the type declarations, we can follow 
> the pattern and be ready...)
> 
> 

-- 
Regards,
Max Carlson
OpenLaszlo.org