Compare-Object for differences in PowerShell - Mini Project: Build & Apply

Compare-Object for differences

📖 Scenario: You work in a small office where you keep two lists of employee names. One list is the current team, and the other is the team from last year. You want to find out who joined or left the team.

🎯 Goal: Build a PowerShell script that uses Compare-Object to find differences between two lists of employee names.

📋 What You'll Learn

Create two arrays called currentTeam and lastYearTeam with exact names

Create a variable called differences to store the comparison result using Compare-Object

Use Compare-Object with the -PassThru parameter to get the differing names

Print the differences variable to show who joined or left

💡 Why This Matters

🌍 Real World

Comparing lists of employees, files, or settings to find changes is common in IT and office work.

💼 Career

Knowing how to use Compare-Object helps in system administration, auditing, and automation tasks.

1

Create the two team lists

Create two arrays called currentTeam and lastYearTeam with these exact names:
currentTeam: "Alice", "Bob", "Charlie", "Diana"
lastYearTeam: "Bob", "Charlie", "Eve", "Frank"

PowerShell

# Create the currentTeam and lastYearTeam arrays with exact names
# Your code here

Need a hint?

Use @("name1", "name2", ...) to create arrays in PowerShell.

2

Compare the two lists

Create a variable called differences that stores the result of Compare-Object comparing $currentTeam and $lastYearTeam with the -PassThru parameter.

PowerShell

$currentTeam = @("Alice", "Bob", "Charlie", "Diana")
$lastYearTeam = @("Bob", "Charlie", "Eve", "Frank")
# Create the differences variable using Compare-Object with -PassThru
# Your code here

Need a hint?

Use Compare-Object -ReferenceObject $lastYearTeam -DifferenceObject $currentTeam -PassThru to get the differing names.

3

Filter differences by side indicator

Use a foreach loop with variables name and side to iterate over Compare-Object output (without -PassThru) comparing $lastYearTeam and $currentTeam. Create two arrays called joined and left to store names who joined (side is '=>') and left (side is '<=') respectively.

PowerShell

$currentTeam = @("Alice", "Bob", "Charlie", "Diana")
$lastYearTeam = @("Bob", "Charlie", "Eve", "Frank")
$differences = Compare-Object -ReferenceObject $lastYearTeam -DifferenceObject $currentTeam -PassThru

# Create joined and left arrays
$joined = @()
$left = @()

# Use foreach loop to fill joined and left
# Your code here

Need a hint?

Use $diff.InputObject and $diff.SideIndicator inside the loop to check each difference.

4

Print who joined and who left

Print the arrays joined and left using Write-Output with these exact messages:
"Joined team: " followed by the joined names separated by commas,
and "Left team: " followed by the left names separated by commas.

PowerShell

$currentTeam = @("Alice", "Bob", "Charlie", "Diana")
$lastYearTeam = @("Bob", "Charlie", "Eve", "Frank")
$differences = Compare-Object -ReferenceObject $lastYearTeam -DifferenceObject $currentTeam -PassThru

$joined = @()
$left = @()

foreach ($diff in Compare-Object -ReferenceObject $lastYearTeam -DifferenceObject $currentTeam) {
    $name = $diff.InputObject
    $side = $diff.SideIndicator
    if ($side -eq '=>') {
        $joined += $name
    } elseif ($side -eq '<=') {
        $left += $name
    }
}

# Print joined and left arrays with messages
# Your code here

Need a hint?

Use Write-Output "Joined team: $($joined -join ', ')" to print the joined names separated by commas.