JSON for human-readable data in IOT Protocols - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does JSON stand for?

JSON stands for JavaScript Object Notation. It is a simple format to store and exchange data in a way that is easy for humans to read and write.

beginner

Why is JSON considered human-readable?

JSON uses plain text with clear structure using braces, brackets, and key-value pairs, making it easy for people to understand and edit without special tools.

beginner

Which characters are used to define an object and an array in JSON?

In JSON, curly braces { } define an object, and square brackets [ ] define an array.

beginner

How are key-value pairs written in JSON?

Key-value pairs in JSON are written as "key": value, where the key is a string in double quotes, followed by a colon and the value.

beginner

What types of values can JSON have?

JSON values can be strings, numbers, objects, arrays, true, false, or null.

Which symbol is used to start a JSON object?

A {

B [

C (

D <

JSON objects start with curly braces { }.

In JSON, how are keys written?

A Double quotes

B Single quotes

C Without quotes

D Backticks

JSON keys must be strings enclosed in double quotes.

Which of these is NOT a valid JSON value?

A true

B 123

C null

D undefined

"undefined" is not a valid JSON value.

What does JSON primarily help with?

A Encrypting data

B Making data human-readable and easy to exchange

C Compressing files

D Running programs

JSON is designed to store and exchange data in a human-readable way.

Which of these is a valid JSON array?

A {"name": "John"}

B (1, 2, 3)

C [1, 2, 3]

D "[1, 2, 3]"

Square brackets [ ] define arrays in JSON.

Explain what JSON is and why it is useful for human-readable data exchange.

Think about how JSON looks and why people like to use it.

Describe the basic syntax rules of JSON including how objects and arrays are represented.

Focus on the symbols and structure used in JSON.

Practice

1. What is the main purpose of JSON in IoT protocols?

easy

A. To store data in a clear, easy-to-read text format

B. To encrypt data for security

C. To compress data for faster transmission

D. To execute commands on devices

Solution

1. Step 1: Understand JSON's role

   JSON is designed to store and share data in a readable text format.

2. Step 2: Compare options

   Only To store data in a clear, easy-to-read text format describes JSON's main purpose correctly; others describe different functions.

3. Final Answer:

   To store data in a clear, easy-to-read text format -> Option A

4. Quick Check:

   JSON = readable data format [OK]

Hint: Remember JSON is for readable data, not encryption or commands [OK]

Common Mistakes:

• Confusing JSON with encryption methods
• Thinking JSON compresses data
• Assuming JSON runs device commands

2. Which of the following is the correct JSON syntax for an object with a key "device" and value "sensor"?

easy

A. {'device': 'sensor'}

B. {device: "sensor"}

C. {"device": "sensor"}

D. ["device": "sensor"]

Solution

1. Step 1: Recall JSON syntax rules

   Keys and string values must be in double quotes, and objects use curly braces.

2. Step 2: Check each option

   {"device": "sensor"} uses double quotes correctly around key and value with curly braces; others have syntax errors.

3. Final Answer:

   {"device": "sensor"} -> Option C

4. Quick Check:

   JSON keys and strings use double quotes [OK]

Hint: Use double quotes for keys and strings in JSON [OK]

Common Mistakes:

• Using single quotes instead of double quotes
• Omitting quotes around keys
• Using square brackets for objects

3. Given the JSON data: {"temperature": 22, "humidity": 45}, what is the value of the key "humidity"?

medium

A. 22

B. 45

C. "humidity"

D. null

Solution

1. Step 1: Identify the key-value pairs

   The JSON object has keys "temperature" with value 22 and "humidity" with value 45.

2. Step 2: Find the value for "humidity"

   The value paired with "humidity" is 45.

3. Final Answer:

   45 -> Option B

4. Quick Check:

   humidity value = 45 [OK]

Hint: Look directly after the key for its value in JSON [OK]

Common Mistakes:

• Confusing key names with values
• Selecting the wrong number
• Assuming null if unsure

4. Identify the error in this JSON snippet: {"status": "active", "count": 10,}

medium

A. Trailing comma after last item

B. Missing quotes around keys

C. Using single quotes instead of double quotes

D. Keys and values are reversed

Solution

1. Step 1: Check JSON syntax rules

   JSON objects cannot have a comma after the last key-value pair.

2. Step 2: Locate the error in the snippet

   The comma after "count": 10 is invalid and causes a syntax error.

3. Final Answer:

   Trailing comma after last item -> Option A

4. Quick Check:

   No trailing commas allowed in JSON objects [OK]

Hint: No comma after last item in JSON objects [OK]

Common Mistakes:

• Leaving a comma after the last pair
• Using single quotes for strings
• Omitting quotes around keys

5. You want to send sensor data with temperature and humidity using JSON. Which JSON structure correctly represents temperature 25 and humidity 60?

hard

A. {"temperature"; 25, "humidity"; 60}

B. ["temperature": 25, "humidity": 60]

C. {"temperature": "25", "humidity": "60"}

D. {"temperature": 25, "humidity": 60}

Solution

1. Step 1: Understand JSON data types

   Numbers should be unquoted for numeric values; strings are quoted.

2. Step 2: Evaluate each option

   {"temperature": 25, "humidity": 60} uses correct syntax with numeric values unquoted and proper colons and commas.

3. Step 3: Check other options

   ["temperature": 25, "humidity": 60] uses brackets incorrectly; A uses semicolons instead of colons; D quotes numbers as strings.

4. Final Answer:

   {"temperature": 25, "humidity": 60} -> Option D

5. Quick Check:

   Numbers unquoted, colons separate keys and values [OK]

Hint: Use curly braces and colons; numbers unquoted in JSON [OK]

Common Mistakes:

• Using square brackets for objects
• Replacing colons with semicolons
• Quoting numeric values unnecessarily