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Reverse Array in ASP

Apr 15

A problem I've ran into numerous times when programming in ASP is that there is no easy way to reverse arrays. With my limited knowledge of other programming languages I believe ASP is the minority of web languages that can't reverse or sort arrays with built in functions. I had also searched high and low on the web for a home brewed function to do this but never had any luck.

Then the other day I ran across this nugget of an article.

Reversing Arrays in ASP:

Here we define our array. In most cases this is done from a database. articlesRev = array( _ "array item 0", _ "array item 1", _ "array item 2", _ "array item 3" _ )
Next we loop through our original array and reverse it. Dim articles() ubnd = UBound(articlesRev) Redim articles(ubnd) for i = 0 to ubnd articles(ubnd - i) = articlesRev(i) next
Finally we write out our array, which is reversed now. for i=0 to ubound(articles) response.Write(articles(i)&"<br>") next

Putting It all together:


articlesRev = array( _
"array item 0", _
"array item 1", _
"array item 2", _
"array item 3" _
)

Dim articles()
ubnd = UBound(articlesRev)
Redim articles(ubnd)
for i = 0 to ubnd
 articles(ubnd - i) = articlesRev(i)
next

for i=0 to ubound(articles)
 response.Write(articles(i)&"<br>")
next

Sources:

http://www.cruto.com/blog/?p=4

Tags: asp ( Add Tag )

Chris Retlich

Wed. April 16 2008, 10:00:19 PM

Or you could just go through the array backwards when you use it.





for i = ubound to 0 step -1


    response.write array(i)


next





or, even reverse the array subscript/index when referencing the array:





for i = 0 to ubound


    response.write array(ubound-i)


next

Neal Grosskopf

Thu. April 17 2008, 10:00:28 AM

Nice suggestions Chris. I tried those out and they are less code and work better!

Neal Grosskopf

Wed. April 23 2008, 11:01:04 AM

The problem I've found which is really quirky is that when you reverse an array using your methods (i.e reverse array and response write it out) and then access that same array later, it is still reversed. One would think that by just looping through and and not changing the array elements values, it would remain how it was initially created. So I had to revert everything back to my initial setup using two separate arrays.

Chris Retlich

Sat. April 26 2008, 10:46:35 PM

It shouldn't be reversed, as you are only reading it backwards and not actually changing the contents. Maybe it is changed somewhere else in the code or maybe you are reading it backwards in both places instead of just the one place?

hey me

Fri. July 11 2008, 9:48:43 AM

for i = 0 to ubound
response.write array(ubound-i)
next
what is ubound????

Neal Grosskopf

Wed. July 16 2008, 11:52:30 AM

ubound means Upper Bound. It essentially returns the total amount of items you have in your array.

Katy Whitton

Wed. June 17 2009, 8:16:22 AM

Thanks a lot for this - it was just what I was looking for!

#8

Fri. April 19, 5:58:30 AM

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Reverse Array in ASP

Apr 15

Reversing Arrays in ASP:

Putting It all together:

Sources:

Replies:

Wed. April 16 2008, 10:00:19 PM

Thu. April 17 2008, 10:00:28 AM

Wed. April 23 2008, 11:01:04 AM

Sat. April 26 2008, 10:46:35 PM

Fri. July 11 2008, 9:48:43 AM

Wed. July 16 2008, 11:52:30 AM

Wed. June 17 2009, 8:16:22 AM

Reply:

Fri. April 19, 5:58:30 AM