JSON operations (ConvertFrom-Json, ConvertTo-Json) in PowerShell

Introduction

JSON operations let you easily change data between text and objects. This helps scripts talk with web services or save data in a simple format.

When you get data from a web API and want to use it in your script.

When you want to save script data in a file that other programs can read.

When you need to send data from your script to another program or service.

When you want to read a JSON file and work with its data inside PowerShell.

When you want to convert PowerShell objects to JSON text for sharing or storage.

Syntax

PowerShell

ConvertFrom-Json [-InputObject] <string> [<CommonParameters>]
ConvertTo-Json [-InputObject] <psobject> [-Depth <int>] [<CommonParameters>]

ConvertFrom-Json turns JSON text into PowerShell objects you can work with.

ConvertTo-Json turns PowerShell objects into JSON text you can save or send.

Examples

This converts JSON text to an object, then prints the name property.

PowerShell

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

This converts a PowerShell object to JSON text and prints it.

PowerShell

$obj = @{name='Bob'; age=25}
$jsonText = $obj | ConvertTo-Json
$jsonText

This converts a JSON array to objects and prints the first item's name.

PowerShell

$jsonText = '[{"item":"apple","qty":5},{"item":"banana","qty":3}]'
$list = $jsonText | ConvertFrom-Json
$list[0].item

Sample Program

This script shows how to convert JSON text to an object, read and change data, then convert it back to JSON text.

PowerShell

$jsonString = '{"city":"Paris","temperature":18}'
# Convert JSON text to object
$weather = $jsonString | ConvertFrom-Json

# Access properties
Write-Output "City: $($weather.city)"
Write-Output "Temperature: $($weather.temperature)°C"

# Change temperature
$weather.temperature = 20

# Convert back to JSON text
$newJson = $weather | ConvertTo-Json
Write-Output $newJson

Important Notes

Use the -Depth parameter with ConvertTo-Json if your object has nested objects deeper than 2 levels.

ConvertFrom-Json only works with valid JSON text. Invalid JSON will cause errors.

JSON keys become object properties you can access with dot notation.

Summary

ConvertFrom-Json changes JSON text into PowerShell objects.

ConvertTo-Json changes PowerShell objects into JSON text.

These commands help scripts work with data from web APIs or files easily.

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