Appending a string to each item of an array - arrays

Question

I have an array and when I try to append a string to it the array converts to a single string.
I have the following data in an array:
$Str
451 CAR,-3 ,7 ,10 ,0 ,3 , 20 ,Over: 41
452 DEN «,40.5,0,7,0,14, 21 ,  Cover: 4
And I want to append the week of the game in this instance like this:
$Str = "Week"+$Week+$Str
I get a single string:
Week16101,NYG,42.5 ,3 ,10 ,3 ,3 , 19 ,Over 43 102,PHI,- 1,14,7,0,3, 24 ,  Cover 4 103,
Of course I'd like the append to occur on each row.

Answer 1

Instead of a for loop you could also use the Foreach-Object cmdlet (if you prefer using the pipeline):
$str = "apple","lemon","toast"
$str = $str | ForEach-Object {"Week$_"}
Output:
Weekapple
Weeklemon
Weektoast

Answer 2

Another option for PowerShell v4+
$str = $str.ForEach({ "Week" + $Week + $_ })

Answer 3

Something like this will work for prepending/appending text to each line in an array.
Set array $str:
$str = "apple","lemon","toast"
$str
apple
lemon
toast
Prepend text now:
for ($i=0; $i -lt $Str.Count; $i++) {
$str[$i] = "yogurt" + $str[$i]
}
$str
yogurtapple
yogurtlemon
yogurttoast
This works for prepending/appending static text to each line. If you need to insert a changing variable this may require some modification. I would need to see more code in order to recommend something.

Answer 4

Another solution, which is fast and concise, albeit a bit obscure.
It uses the regex-based -replace operator with regex '^' which matches the position at the start of each input string and therefore effectively prepends the replacement string to each array element (analogously, you could use '$' to append):
# Sample array.
$array = 'one', 'two', 'three'
# Prepend 'Week ' to each element and create a new array.
$newArray = $array -replace '^', 'Week '
$newArray then contains 'Week one', 'Week two', 'Week three'
To show an equivalent foreach solution, which is syntactically simpler than a for solution (but, like the -replace solution above, invariably creates a new array):
[array] $newArray = foreach ($element in $array) { 'Week ' + $element }
Note: The [array] cast is needed to ensure that the result is always an array; without it, if the input array happens to contain just one element, PowerShell would assign the modified copy of that element as-is to $newArray; that is, no array would be created.
As for what you tried:
"Week"+$Week+$Str
Because the LHS of the + operation is a single string, simple string concatenation takes place, which means that the array in $str is stringified, which by default concatenates the (stringified) elements with a space character.
A simplified example:
PS> 'foo: ' + ('bar', 'baz')
foo: bar baz
Solution options:
For per-element operations on an array, you need one of the following:
A loop statement, such as foreach or for.
Michael Timmerman's answer shows a for solution, which - while syntactically more cumbersome than a foreach solution - has the advantage of updating the array in place.
A pipeline that performs per-element processing via the ForEach-Object cmdlet, as shown in Martin Brandl's answer.
An expression that uses the .ForEach() array method, as shown in Patrick Meinecke's answer.
An expression that uses an operator that accepts arrays as its LHS operand and then operates on each element, such as the -replace solution shown above.
Tradeoffs:
Speed:
An operator-based solution is fastest, followed by for / foreach, .ForEach(), and, the slowest option, ForEach-Object.
Memory use:
Only the for option with indexed access to the array elements allows in-place updating of the input array; all other methods create a new array.[1]
[1] Strictly speaking, what .ForEach() returns isn't a .NET array, but a collection of type [System.Collections.ObjectModel.Collection[psobject]], but the difference usually doesn't matter in PowerShell.