[Web4lib] global variables versus local variables

[Erik Adams]

> Why is it more efficient to define a variable within a
> sub-routine?

It isn't more efficient at execute time; it's more efficient at coding,
debugging, and maintenance time.  If simple variables (like loop
counters) are locally scoped, you don't have to worry about one function
modifying another's variables, potentially breaking an important test.
And, with modern computers, the performance loss is miniscule.

However, if your variable is expensive to create (time and memory
intensive), then the performance issues will overtake the coding
concerns.  For example, if you're coding for IE and creating a lot of
ActiveX objects in Javascript, you might be better off creating a global
instance and just being careful to reset it locally.

Erik Y. Adams
Electronic Resources Librarian
Sheppard, Mullin, Richter & Hampton
eadams at sheppardmullin.com
(213)617-5429 / Fax: (213)620-1398 



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