JSON as standard format in Rest API - Step-by-Step Execution

Concept Flow - JSON as standard format

Start: Data to send

↓

Convert data to JSON

↓

Send JSON in API request

↓

Receive JSON response

↓

Parse JSON response

↓

Use data in application

Data is converted to JSON, sent via API, received as JSON, then parsed for use.

Execution Sample

Rest API

POST /api/data HTTP/1.1
Content-Type: application/json

{"name":"Alice","age":30}

This sends a JSON object with name and age in an API POST request.

Execution Table

Step	Action	Data State	Result
1	Prepare data object	{"name": "Alice", "age": 30}	Data ready to convert
2	Convert to JSON string	{"name":"Alice","age":30}	JSON string created
3	Send API request with JSON	JSON string in HTTP body	Request sent to server
4	Server receives JSON	JSON string	Server parses JSON
5	Server sends JSON response	{"status":"success"}	Response sent
6	Client receives response	{"status":"success"}	Response ready to parse
7	Parse JSON response	{"status": "success"}	Data ready to use

💡 Process ends after JSON response is parsed and data is ready.

Variable Tracker

Variable	Start	After 1	After 2	After 3	After 4	After 5	Final
data_object	{}	{"name": "Alice", "age": 30}	{"name": "Alice", "age": 30}	{"name": "Alice", "age": 30}	{"name": "Alice", "age": 30}	{"name": "Alice", "age": 30}	{"name": "Alice", "age": 30}
json_string	""	""	{"name":"Alice","age":30}	{"name":"Alice","age":30}	{"name":"Alice","age":30}	{"status":"success"}	{"status":"success"}
response_data	null	null	null	null	null	{"status":"success"}	{"status": "success"}

Key Moments - 3 Insights

Why do we convert data to a JSON string before sending?

Because APIs send data as text, converting to JSON string makes the data easy to send and understand by both client and server (see execution_table step 2).

What happens if the server sends back JSON but we don't parse it?

Without parsing, the response stays as a string and can't be used as data in the program (see execution_table step 7).

Is JSON the only format for API data?

No, but JSON is the most common because it is simple, readable, and supported everywhere (concept_flow shows JSON as the standard).

Visual Quiz - 3 Questions

Look at the execution_table, what is the data state after step 3?

A JSON string in HTTP body

B Data object before conversion

C Parsed response data

D Empty string

💡 Hint

Check the 'Data State' column in row for step 3 in execution_table.

At which step does the server parse the JSON?

A Step 2

B Step 4

C Step 6

D Step 7

💡 Hint

Look for 'Server parses JSON' in the 'Result' column of execution_table.

If the client skips parsing the JSON response, what happens to response_data variable?

A It stays as a JSON string

B It becomes null

C It becomes a data object

D It causes an error

💡 Hint

See variable_tracker for response_data before and after parsing.

Concept Snapshot

JSON is a text format to send data in APIs.
Convert data objects to JSON strings before sending.
Server and client parse JSON strings back to data.
JSON is easy to read and widely supported.
Always parse JSON responses to use data in code.

Full Transcript

This visual trace shows how data is prepared as a JSON object, converted to a JSON string, sent in an API request, received by the server, parsed, and then a JSON response is sent back and parsed by the client. Each step changes the data state from object to string and back to object. Beginners often wonder why conversion and parsing are needed; this trace clarifies that APIs communicate using text, so JSON strings are the standard format. Parsing is essential to use the data after receiving it. JSON is the most common format because it is simple and supported everywhere.

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