JSON Quiz Test Online (30 random Questions) 2026

This quick 30-minute challenge consists of 30 random multiple-choice questions designed to test your knowledge across various JSON topics, including the introduction to JSON, JSON syntax and basics, data types, operations in JavaScript, APIs and JSON, advanced structures, JSON Schema, tools and debugging, as well as performance and security considerations. Whether you’re new to JSON or looking to refine your skills, this quiz will enhance your understanding of JSON’s role in modern web development.

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30 Minutes JSON Quiz Test Online

Welcome to the JSON Quiz! This quick 30-minute challenge consists of 30 random multiple-choice questions designed to test your knowledge across various JSON topics, including the introduction to JSON, JSON syntax and basics, data types, operations in JavaScript, APIs and JSON, advanced structures, JSON Schema, tools and debugging, as well as performance and security considerations. Whether you're new to JSON or looking to refine your skills, this quiz will enhance your understanding of JSON's role in modern web development.

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1. What does a JSON array of objects look like?

A) { "object1": "value1", "object2": "value2" }

B) { "array": [ "value1", "value2" ] }

C) [ "object1", "object2" ]

D) [ { "key": "value" }, { "key": "value" } ]

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2. How do you handle very large JSON data efficiently in JavaScript?

A) Split the JSON file into multiple smaller files

B) Load the entire JSON object in memory

C) Both B and C

D) Use streaming parsers like JSONStream

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3. How does JSON web encryption (JWE) enhance JSON security?

A) It converts JSON to binary format

B) It compresses JSON data

C) It adds authentication to JSON

D) It encrypts JSON payloads for secure transmission

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4. Which of the following methods can help trace JSON parsing errors in JavaScript?

A) console.parse()

B) JSON.log()

C) try...catch blocks around JSON.parse()

D) window.debug()

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5. Which JSON data type is used to group key-value pairs?

A) Object

B) Array

C) String

D) Number

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6. What is the use of the $ref keyword in JSON Schema?

A) To include reusable schema definitions

B) To reference external files

C) To define a default value

D) To specify required properties

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7. Which extension helps debug JSON in Visual Studio Code?

A) Prettier

B) REST Client

C) JSON Formatter

D) JSON Tools

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8. What does the properties keyword do in JSON Schema?

A) Defines the maximum number of keys in an object

B) Defines the keys allowed in an object

C) Specifies the data type of an array

D) Lists all required fields in an object

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9. How are floating-point numbers represented in JSON?

A) 1.23f

B) float(1.23)

C) 1.23

D) "1.23"

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10. How is JSON used in data interchange for machine learning models?

A) To train models directly

B) To compile machine learning libraries

C) To render visualizations

D) To serialize model configurations and results

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11. What is the result of running JSON.parse('{"key":value}') in JavaScript?

A) ReferenceError

B) null

C) SyntaxError: Unexpected identifier

D) A key-value pair object

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12. Which of the following is the correct way to represent an empty JSON object?

A) []

B) null

C) {}

D) ""

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13. How do you represent a key-value pair where the value is an array?

A) [ { "key": "value1" } ]

B) { "key": { "value1": "value2" } }

C) { "key": [ "value1", "value2" ] }

D) { "key": "value1", "value2" }

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14. What does the type keyword accept for mixed data types?

A) A single string

B) An array of types

C) A boolean flag

D) A numeric range

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15. What happens when a fetch() request encounters a network error?

A) Returns an empty object

B) Continues execution without errors

C) Throws a TypeError

D) Returns undefined

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16. Which of the following ensures JSON data is safe from injection attacks?

A) Using only numeric data

B) Input validation and sanitization

C) Minification

D) Removing all keys from JSON

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17. How do you represent a null value in JSON?

A) (null)

B) "null"

C) NULL

D) null

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18. What does the title keyword do in JSON Schema?

A) Sets a required field

B) Specifies a string pattern

C) Gives a short label to the schema or property

D) Provides a description of the schema

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19. What does the Content-Type header specify in an API request?

A) The format of the data being sent or expected

B) The HTTP method to be used

C) The status of the response

D) The size of the request body

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20. What does a JSON path debugger do?

A) Extracts specific values from JSON

B) Beautifies JSON

C) Validates JSON syntax

D) Converts JSON to CSV

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21. What happens if a key in a JSON object contains special characters?

A) The key must be enclosed in double quotes

B) The key is ignored

C) The special characters are escaped automatically

D) It throws an error

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22. How do you handle errors in a fetch() request?

A) Using try...catch blocks or then().catch() methods

B) Using the error property of the response

C) Using fetchError() function

D) Errors cannot be handled in fetch()

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23. Which of the following JSON data types is valid?

A) Object

B) Float

C) String

D) All of the above

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24. What will JSON.stringify({ key: undefined }) return?

A) {"key": null}

B) {"key": "undefined"}

C) {}

D) Throws an error

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25. How do you access the name of the first employee in the JSON structure { "department": { "employees": [ { "name": "John" }, { "name": "Alice" } ] } }?

A) employees[0].name

B) department.employees[0].name

C) department.employees[1].name

D) department[employees][name]

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26. How do you specify a format for email validation in JSON Schema?

A) type: "email"

B) pattern: "/[email]/"

C) format: "email"

D) validate: "email"

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27. Why is it important to validate JSON data received from external sources?

A) To compress JSON

B) To prevent unexpected errors and security vulnerabilities

C) To convert JSON into JavaScript objects

D) To improve parsing speed

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28. How do you specify a pattern for a string in JSON Schema?

A) regex

B) match

C) pattern

D) format

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29. Which of the following is true about JSON numbers?

A) They cannot be negative

B) They support both integers and floats

C) They must include a decimal point

D) They must be enclosed in double quotes

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30. Which of these is a valid JSON array of strings?

A) ["apple", "banana", "cherry"]

B) ['apple', 'banana', 'cherry']

C) [apple, banana, cherry]

D) ["apple", 'banana', "cherry"]

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