join range operator

Reverse String
Reverse String in PowerShell 
function ReverseString([string] $String) {
    -join $String[$String.Length..0]
}

Using range from $String.Length..0, we created a range of indices from the length down to 0. Apply the range to the string give us an array of object, in this case an array of char in reverse order of the original string. Then we use -join to concatenate these character back into a single string, effectively reversing the input string.

Note : Technically speaking the valid range is from ($String.Length-1)..0 due to the nature of 0 based index. However PowerShell is forgiving in these cases, and this convient feature allows simplified code, making it more concise and readable. Whenever you need precise range of indices, make sure to use the correct range.

Range operator.

Join operator.

6th Nov 2024 · Found it useful?

Other Approaches to Reverse String in PowerShell

Other ways our community solved this exercise
function ReverseString([string] $String) {
    $charArray = $String.ToCharArray()
    [array]::Reverse($charArray)
    -join $charArray
}
built-in reverse

Using the built-in reverse method of the array class. 

function ReverseString([string] $String) {
    $strBuilder = [System.Text.StringBuilder]::new()
    foreach ($i in ($String.Length - 1)..0) {
        [void] $strBuilder.Append($String[$i])
    }
    $strBuilder.ToString()
}
string builder

Build a new string using string builder. 

function ReverseString([char[]] $String) {
    $last = $String.Count - 1
    $mid  = [Math]::Ceiling($String.Count / 2)
    for ($i = 0; $i -lt $mid; $i++) {
        $String[$i], $String[$last - $i] = $String[$last - $i], $String[$i]
    }
    -join $String
}
reverse in place

Reverse the char array in place.