Loop through all computers in an active directory domain

AllComputers.ps1

$ADDomain = 'domain.local'

if((Get-ADDomain -Current LocalComputer) -like "$ADDomain"){
    Write-Host "Credentials will be inherited from logged in session"
    $ADDomain_Obj = Get-ADDomain $ADDomain
} else {
    $Credential=  Get-Credential -Message "Enter credentials for $ADDomain"
    $ADDomain_Obj = Get-ADDomain $ADDomain -Credential $Credential
}

$DC_OU = $ADDomain_Obj.DomainControllersContainer
$PDC   = $ADDomain_Obj.InfrastructureMaster
$Domain_Controllers = get-adcomputer -searchbase $DC_OU -filter * -Server $PDC

$PingTimes = @{}
foreach($Domain_Controller in $Domain_Controllers) {
    $PingTimes.add([string]($Domain_Controller.DNSHostName), [int](Test-NetConnection -ComputerName ($Domain_Controller).DNSHostName).PingReplyDetails.RoundTripTime)
}

$PingTimes = $PingTimes | Sort-Object
$SortedDCList = $PingTimes.Keys
$QuickestDC = $SortedDCList | Select -First 1
$AllComputers = Get-ADComputer -Server $QuickestDC -Filter *

foreach($Computer in $AllComputers) {
    write-host $($AllComputers.DNSHostName) # Your stuff goes here
}