[Javascript] dynamic var names

[Scott Reynen]

On Aug 7, 2007, at 4:59 PM, Terry Riegel wrote:

> I have always called this indirection, and have found several uses  
> for it. Not sure about js but I have used it on several server side  
> projects. Here is a quick outline of one such usage.
>
> I had a user editable table that needed quite bit of processing for  
> each row in the table. I needed a way to cache the results. So I  
> created (via indirection) a variable whose name was the same as the  
> ID from each row.
>
> So I needed a way to flag that a rows processing had been cached. I  
> created a variable whose name was the row ID. Since this ID was  
> assigned in the user editable table I had to use indirection to  
> read/write to the variable.
>
> It is a little confusing, and Javascript may have better ways of  
> doing this.

I think most scripting languages use hashes, a.k.a. associate arrays,  
to do something like this, where it's not really necessary that a  
variable name be defined dynamically, only that some sort of named  
reference to a value be defined dynamically.  A dynamic array key,  
e.g. rowIsCached[rowId] = true, works just as well as a dynamic  
variable name in this case, and removes the risk of naming conflicts  
with other variables or reserved words.  I think associative arrays  
and dynamic variable names are both specific forms of indirection, a  
very general concept of using names/symbols to refer to things  
indirectly.  Email addresses are another common example of indirection.

Peace,
Scott