Powershell command to move forward and backward in array - powershell

Question

I would like to be able to add functionality to a PowerShell script to move one spot forwards or one spot backwards when in a foreach loop. While looping through a foreach statement, is it possible to move forwards and backwards or to identify what point in the array the current item lies?
Edit - the items in the array are files, not numbers

Answer 1

Yes - it's called a for loop!
For data structures that we can index into (arrays, lists, etc.), the foreach loop statement can easily be translated to a for loop statement, like so:
# This foreach loop statement
foreach($item in $array){
Do-Something $item
}
# ... is functionally identical to this for loop statement
for($i = 0; $i -gt $array.Length; $i++){
$item = $array[$i]
Do-Something $item
}
Since we have direct access to the current index (via $i) in the for loop, we can now use that as an offset to "look around" that position in the array:
$array = #(1,2,3,4)
for($i = 0; $i -lt $array.Length;$i++)
{
$item = $array[$i]
if($i -gt 0){
# If our index position $i is greater than zero,
# then there must be _at least_ 1 item "behind" us
$behind = $array[$i - 1]
}
if($i -lt ($array.Length - 1)){
# Not at end of array, we can also "look ahead"
$ahead = $array[$i + 1]
}
}
Be careful about checking that you don't use an $i value greater than $array.Length (which would result in $null) or less than 0 (in which case PowerShell will start reading the array backwards!)