JSON as standard format in Rest API - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does JSON stand for?

JSON stands for JavaScript Object Notation. It is a lightweight format to store and exchange data.

beginner

Why is JSON commonly used in REST APIs?

JSON is easy to read and write for humans and machines. It is language-independent and works well for data exchange between servers and clients.

beginner

What data types can JSON represent?

JSON can represent strings, numbers, objects (key-value pairs), arrays, booleans (true/false), and null.

beginner

How is a JSON object structured?

A JSON object is enclosed in curly braces { } and contains key-value pairs. Keys are strings, and values can be any JSON data type.

beginner

What is a common mistake when writing JSON?

A common mistake is using single quotes instead of double quotes for keys or strings. JSON requires double quotes for all keys and string values.

Which of these is a valid JSON data type?

A Array

B Function

C Undefined

D Symbol

JSON supports arrays, but not functions, undefined, or symbols.

In JSON, how must keys be written?

A With double quotes

B With single quotes

C Without quotes

D With backticks

JSON keys must always be enclosed in double quotes.

What is the main reason JSON is used in REST APIs?

A It supports functions

B It runs faster than XML

C It is easy to read and exchange data

D It is binary format

JSON is popular because it is simple and easy to read and exchange data.

Which symbol encloses a JSON array?

A {}

B []

C ()

D <>

JSON arrays are enclosed in square brackets [].

Which of these is NOT valid JSON?

A {"name": "Alice"}

B {"age": 30}

C {"isStudent": false}

D {name: "Bob"}

Keys must be in double quotes, so {name: "Bob"} is invalid.

Explain why JSON is the standard format for data exchange in REST APIs.

Think about what makes data easy to share between different programs.

Describe the structure of a JSON object and how it differs from a JSON array.

Compare the symbols and content inside JSON objects and arrays.

Practice

1. What is the main reason REST APIs use JSON as their standard format?

easy

A. Because JSON is easy to read and write for both humans and machines

B. Because JSON requires special software to understand

C. Because JSON is a binary format

D. Because JSON only supports numbers

Solution

1. Step 1: Understand JSON format

   JSON is a text-based format that uses simple syntax with objects and arrays.

2. Step 2: Identify why REST APIs prefer JSON

   REST APIs use JSON because it is easy for humans to read and easy for machines to parse.

3. Final Answer:

   Because JSON is easy to read and write for both humans and machines -> Option A

4. Quick Check:

   JSON is text-based and readable [OK]

Hint: JSON is popular because it's simple and readable [OK]

Common Mistakes:

• Thinking JSON is binary
• Believing JSON needs special software
• Assuming JSON only supports numbers

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

easy

A. {"name" = "Alice"}

B. {name: "Alice"}

C. ["name": "Alice"]

D. {"name": "Alice"}

Solution

1. Step 1: Recall JSON object syntax

   JSON objects use curly braces with keys and values as strings, keys must be in double quotes.

2. Step 2: Check each option

   {"name": "Alice"} uses double quotes correctly around key and value, with colon separator.

3. Final Answer:

   {"name": "Alice"} -> Option D

4. Quick Check:

   Keys and strings in double quotes [OK]

Hint: Keys and string values must be in double quotes [OK]

Common Mistakes:

• Omitting quotes around keys
• Using square brackets for objects
• Using equals sign instead of colon

3. Given this JSON response from a REST API:

{"status": "success", "data": [10, 20, 30]}

What is the value of the key "data"?

medium

A. "success"

B. [10, 20, 30]

C. 10

D. {"status": "success"}

Solution

1. Step 1: Identify the key "data" in JSON

   The key "data" holds an array with values 10, 20, and 30.

2. Step 2: Match the value to the options

   [10, 20, 30] correctly shows the array [10, 20, 30].

3. Final Answer:

   [10, 20, 30] -> Option B

4. Quick Check:

   Key "data" = array [10, 20, 30] [OK]

Hint: Look for the key and read its value exactly as shown [OK]

Common Mistakes:

• Confusing key "status" value with "data"
• Picking a single number instead of the array
• Choosing the whole JSON object as value

4. You receive this JSON string from an API:

{"user": "Bob", "age": 25,}

What is wrong with this JSON?

medium

A. Trailing comma after the last item is invalid

B. Keys must be numbers, not strings

C. Values cannot be numbers

D. Missing square brackets around the object

Solution

1. Step 1: Check JSON syntax rules

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

2. Step 2: Identify the error in the string

   The comma after "age": 25 is invalid and causes a syntax error.

3. Final Answer:

   Trailing comma after the last item is invalid -> Option A

4. Quick Check:

   No trailing commas allowed in JSON objects [OK]

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

Common Mistakes:

• Thinking keys must be numbers
• Believing numbers are invalid values
• Adding brackets incorrectly

5. You want to send a JSON payload to a REST API with user info: name "Eve", age 28, and hobbies as an array of "reading" and "swimming". Which JSON is correct?

hard

A. {"name": "Eve", "age": 28, "hobbies": "reading, swimming"}

B. {"name": Eve, "age": "28", "hobbies": ("reading", "swimming")}

C. {"name": "Eve", "age": 28, "hobbies": ["reading", "swimming"]}

D. {"name": "Eve", "age": 28, "hobbies": {"reading", "swimming"}}

Solution

1. Step 1: Check correct JSON types for each field

   Name is a string, age is a number, hobbies is an array of strings.

2. Step 2: Validate each option's syntax

   {"name": "Eve", "age": 28, "hobbies": ["reading", "swimming"]} correctly uses double quotes for strings, numbers without quotes, and square brackets for array.

3. Final Answer:

   {"name": "Eve", "age": 28, "hobbies": ["reading", "swimming"]} -> Option C

4. Quick Check:

   Strings in quotes, numbers plain, arrays in brackets [OK]

Hint: Use quotes for strings, brackets for arrays, no quotes for numbers [OK]

Common Mistakes:

• Using parentheses instead of brackets for arrays
• Not quoting string values
• Putting numbers in quotes unnecessarily