Parsing Function return in PowerShell Script

Question

I am trying to parse the response from one of the functions in PowerShell Script and based on the response I have to make some decision.

The function is returning JSON object successfully but not able to parse the response from the function. I need to check if validnodes count is 0 or not.

      [String[]] $NodeList = 'a1572dev00e001','a1572dev00q001'


$Response = Get-Nodes
Write-Output "Response $Response"
        $JSRes = $Response | ConvertFrom-Json
        Write-Output "Parsing response $JSRes"
        #$Result = "success"

        if($JSRes.ValidNodes.Count -gt 0)
            {
                 Write-Output "$JSRes.ValidNodes"
                 $Result = "success"
                 

            }
            else
                {
                    Write-Output "All nodes are Invalid"
                    Write-Output "Invalid Nodes: $JSRes.Invalid"
                    $Result = "failed"
                    $ErrorMessage = "All nodes are Invalid"
    
            }
        Write-Output $Result


#Function
function Get-Nodes
{
    $ValidNodes=@()
    $InvalidNodes=@()

foreach($Node in $NodeList)
{
    if(Get-ADComputer -filter {Name -eq $Node})
    {
        $ValidNodes +=$Node
    }
    else
    {
        $InvalidNodes +=$Node
    }
}
    $JRes = @{"ValidNodes"=$ValidNodes;"Invalid"=$InvalidNodes} | ConvertTo-Json -Compress
    Write-Output $JRes 
    return $JRes
}

Output:

Response {"ValidNodes":["a1572dev00e001","a1572dev00q001"],"Invalid":[]} {"ValidNodes":["
a1572dev00e001","a1572dev00q001"],"Invalid":[]}
Parsing response 
All nodes are Invalid
Invalid Nodes: 
failed

Answer 1

One issue is you are outputting the $Jres twice.

Write-Output $JRes 
return $JRes

These effectively do the exact same thing. Next, you're using ConvertFrom-String when it seems you should be using ConvertFrom-Json

$JSON = $Response | ConvertFrom-String

Finally, you're trying to output $ValidNodes and $InvalidNodes that only exist in your function. Change these to $JSON.ValidNodes and $JSON.InvalidNodes

One more suggestion is to parameterize the Nodelist so you can just pass the nodes to the function.

#Function
function Get-Nodes
{
    Param([string[]]$nodelist)
    $ValidNodes=@()
    $InvalidNodes=@()

foreach($Node in $NodeList)
{
    if(Get-ADComputer -filter {Name -eq $Node})
    {
        $ValidNodes +=$Node
    }
    else
    {
        $InvalidNodes +=$Node
    }
}
    $JRes = @{"ValidNodes"=$ValidNodes;"Invalid"=$InvalidNodes} | ConvertTo-Json -Compress
    $JRes 
}

$Response = Get-Nodes a1572dev00e001,a1572dev00q001

Write-Output "Response $Response"
$JSON = $Response | ConvertFrom-Json
Write-Output "Parsing response $JSON"

if($JSON.ValidNodes.Count -gt 0)
    {
            Write-Output "Valid Nodes: $($JSON.ValidNodes)"
            $Result = "success"
             
    }
    else
    {
            Write-Output "All nodes are Invalid"
            Write-Output "Invalid Nodes: $($JSON.InValidNodes)"
            $Result = "failed"
            $ErrorMessage = "All nodes are Invalid"

    }
Write-Output $Result