JSON operations (ConvertFrom-Json, ConvertTo-Json) in PowerShell - Mini Project: Build & Apply

JSON operations (ConvertFrom-Json, ConvertTo-Json)

📖 Scenario: You work in a small company that stores employee information in JSON format. You want to read this data, update it, and then save it back as JSON.

🎯 Goal: Learn how to convert JSON text into PowerShell objects using ConvertFrom-Json, modify the data, and then convert it back to JSON text using ConvertTo-Json.

📋 What You'll Learn

Create a JSON string variable with employee data

Convert the JSON string to a PowerShell object

Add a new employee to the object

Convert the updated object back to JSON and display it

💡 Why This Matters

🌍 Real World

Many systems use JSON to store and exchange data. PowerShell scripts often need to read, update, and write JSON data for automation tasks.

💼 Career

Understanding JSON operations in PowerShell is useful for IT administrators, DevOps engineers, and automation specialists who manage configurations and data in JSON format.

1

Create a JSON string with employee data

Create a variable called jsonData and assign it this exact JSON string: '{"employees":[{"name":"Alice","age":30},{"name":"Bob","age":25}]}'

PowerShell

# Create a variable called jsonData with the given JSON string
# Your code here

Hint

Use single quotes around the JSON string to avoid escaping double quotes inside.

2

Convert JSON string to PowerShell object

Use ConvertFrom-Json to convert jsonData into a variable called employeeObj.

PowerShell

$jsonData = '{"employees":[{"name":"Alice","age":30},{"name":"Bob","age":25}]}'
# Convert jsonData to employeeObj using ConvertFrom-Json
# Your code here

Hint

Use $employeeObj = ConvertFrom-Json $jsonData to convert the JSON string.

3

Add a new employee to the object

Add a new employee with name "Charlie" and age 28 to the employees array inside employeeObj.

PowerShell

$jsonData = '{"employees":[{"name":"Alice","age":30},{"name":"Bob","age":25}]}'
$employeeObj = ConvertFrom-Json $jsonData
# Add new employee to employeeObj.employees
# Your code here

Hint

Use $employeeObj.employees += @{name='Charlie'; age=28} to add the new employee.

4

Convert the updated object back to JSON and display it

Use ConvertTo-Json to convert employeeObj back to JSON and print it with Write-Output.

PowerShell

$jsonData = '{"employees":[{"name":"Alice","age":30},{"name":"Bob","age":25}]}'
$employeeObj = ConvertFrom-Json $jsonData
$employeeObj.employees += @{name='Charlie'; age=28}
# Convert employeeObj back to JSON and print it
# Your code here

Hint

Use $jsonOutput = ConvertTo-Json $employeeObj and then Write-Output $jsonOutput.

Practice

1. What does the PowerShell cmdlet ConvertFrom-Json do?

easy

A. It converts JSON text into PowerShell objects.

B. It converts PowerShell objects into JSON text.

C. It formats JSON text for better readability.

D. It validates JSON syntax without conversion.

Solution

1. Step 1: Understand the purpose of ConvertFrom-Json

   This cmdlet takes JSON formatted text and turns it into PowerShell objects you can work with.

2. Step 2: Differentiate from ConvertTo-Json

   ConvertTo-Json does the opposite by turning objects into JSON text, so it is not the correct answer here.

3. Final Answer:

   It converts JSON text into PowerShell objects. -> Option A

4. Quick Check:

   ConvertFrom-Json = JSON text to objects [OK]

Hint: ConvertFrom-Json = JSON text to objects [OK]

Common Mistakes:

• Confusing ConvertFrom-Json with ConvertTo-Json
• Thinking it only formats JSON without conversion
• Assuming it validates JSON syntax only

2. Which of the following is the correct syntax to convert a JSON string stored in variable $jsonText into a PowerShell object?

easy

A. ConvertTo-Json $jsonText

B. $jsonText | ConvertTo-Json

C. ConvertFrom-Json $jsonText -Compress

D. $jsonText | ConvertFrom-Json

Solution

1. Step 1: Identify the correct cmdlet for JSON to object conversion

   ConvertFrom-Json converts JSON text to PowerShell objects, so it is the right cmdlet.

2. Step 2: Check the syntax for using pipeline

   Using $jsonText | ConvertFrom-Json is the correct way to pipe the JSON string into the cmdlet.

3. Final Answer:

   $jsonText | ConvertFrom-Json -> Option D

4. Quick Check:

   Pipe JSON string to ConvertFrom-Json [OK]

Hint: Pipe JSON string to ConvertFrom-Json for conversion [OK]

Common Mistakes:

• Using ConvertTo-Json instead of ConvertFrom-Json
• Trying to call ConvertFrom-Json without pipeline incorrectly
• Confusing parameter order or cmdlet usage

3. What is the output of this PowerShell code?

$json = '{"name":"Alice","age":30}'
$obj = $json | ConvertFrom-Json
$obj.age

medium

A. Error: Cannot convert string to object

B. 30

C. age

D. "30"

Solution

1. Step 1: Convert JSON string to object

   The JSON string contains a property "age" with value 30 (number). ConvertFrom-Json creates an object with property age = 30.

2. Step 2: Access the age property

   Accessing $obj.age returns the numeric value 30, not a string or error.

3. Final Answer:

   30 -> Option B

4. Quick Check:

   Property age value = 30 [OK]

Hint: ConvertFrom-Json creates objects; access properties directly [OK]

Common Mistakes:

• Expecting age as a string with quotes
• Thinking the output is the property name 'age'
• Assuming conversion error occurs

4. What is the output of this PowerShell code?

$json = '{"name":"Bob","age":25}'
$obj = ConvertFrom-Json $json
Write-Output $obj.name

medium

A. Bob

B. "Bob"

C. name

D. Error: Cannot convert string to object

Solution

1. Step 1: Convert JSON string to object

   The JSON string contains a property "name" with value Bob (string). ConvertFrom-Json creates an object with property name = Bob.

2. Step 2: Access the name property

   Accessing $obj.name returns the string value Bob, not a quoted string or error.

3. Final Answer:

   Bob -> Option A

4. Quick Check:

   Property name value = Bob [OK]

Hint: ConvertFrom-Json creates objects; access properties directly [OK]

Common Mistakes:

• Expecting output as a string with quotes
• Thinking the output is the property name 'name'
• Assuming positional argument causes conversion error

5. You have a PowerShell object:

$person = @{ Name = "Eve"; Age = 28; Skills = @("PowerShell", "JSON") }

Which command correctly converts this object to JSON text with indentation for readability?

hard

A. $person | ConvertTo-Json -Depth 2 -Compress

B. $person | ConvertTo-Json -Depth 2 -Pretty

C. $person | ConvertTo-Json -Depth 2

D. ConvertTo-Json $person -Depth 2 -Compress

Solution

1. Step 1: Understand ConvertTo-Json parameters

   ConvertTo-Json converts objects to JSON text. The -Depth parameter controls how deep nested objects are converted.

2. Step 2: Identify correct parameter for indentation

   By default, ConvertTo-Json outputs indented JSON. The -Compress parameter removes whitespace, so it is not desired. There is no -Pretty parameter.

3. Final Answer:

   $person | ConvertTo-Json -Depth 2 -> Option C

4. Quick Check:

   Default output is indented JSON [OK]

Hint: Use ConvertTo-Json with -Depth; default output is indented [OK]

Common Mistakes:

• Using -Compress removes indentation
• Using non-existent -Pretty parameter
• Not setting -Depth for nested objects