JSON Quiz Test Online (30 random Questions) 2025

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.

1 / 30

1. What is JSON Schema?

A) A method to minify JSON files

B) A specification to define and validate the structure of JSON data

C) A library to parse JSON data

D) A format to store JSON data

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

A) Input validation and sanitization

B) Removing all keys from JSON

C) Using only numeric data

D) Minification

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3. What is the result of JSON.parse('null') in JavaScript?

A) Returns null

B) Returns undefined

C) Throws a syntax error

D) Converts to the string "null"

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4. Which method is used to convert a JavaScript object into a JSON string?

A) JSON.encode()

B) JSON.toString()

C) JSON.parse()

D) JSON.stringify()

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5. What is the purpose of the fetch() method in JavaScript?

A) To encrypt data

B) To parse JSON strings

C) To send emails

D) To make HTTP requests to APIs

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6. Which of the following is a valid JSON string?

A) Hello

B) 'Hello'

C) "Hello"

D) “Hello”

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7. What is the purpose of an API key in requests?

A) To specify the API version

B) To encrypt the request data

C) To authenticate the client

D) To indicate the request priority

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

A) Combines multiple schemas

B) Ensures that the data matches exactly one of the specified schemas

C) Requires all listed schemas to match

D) Validates against one specific type

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9. Which of the following JSON strings can be parsed without error?

A) '{name: "John", age: 30}'

B) '{"name": John, "age": 30}'

C) '{name: John, age: 30}'

D) '{"name": "John", "age": 30}'

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10. What is the output of the code: JSON.stringify({ key: undefined, key2: "value" });

A) {"key2": "value"}

B) {"key": null, "key2": "value"}

C) {"key": "", "key2": "value"}

D) {"key": undefined, "key2": "value"}

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11. How are negative numbers represented in JSON?

A) -123

B) negative123

C) [123]

D) (123)

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

A) format

B) pattern

C) match

D) regex

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13. How can you handle errors when parsing JSON in JavaScript?

A) JSON parsing cannot produce errors

B) Checking the JSON string with isValid()

C) Using a try...catch block

D) Using the JSON.validate() method

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

A) department.employees[0].name

B) department.employees[1].name

C) department[employees][name]

D) employees[0].name

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15. Can JSON keys have spaces?

A) Yes, with quotes

B) No

C) Yes, without quotes

D) Only in arrays

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16. What will be the output of the code: JSON.stringify({ key1: "value1", key2: function() { return "value2"; } });

A) {"key1": "value1", "key2": "value2"}

B) Throws an error

C) {"key1": "value1"}

D) {"key1": "value1", "key2": null}

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

A) 1.23f

B) "1.23"

C) float(1.23)

D) 1.23

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

A) Split the JSON file into multiple smaller files

B) Use streaming parsers like JSONStream

C) Both B and C

D) Load the entire JSON object in memory

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19. What is a common vulnerability associated with parsing untrusted JSON?

A) JSON Injection

B) JSON Brute Force

C) JSON Flooding

D) JSON Parsing Loops

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20. What is the output of JSON.stringify([1, undefined, 2])?

A) "[1, , 2]"

B) Throws a TypeError

C) "[1, null, 2]"

D) "[1, undefined, 2]"

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21. Which of the following is NOT a valid use case of JSON.stringify()?

A) Serializing objects with circular references

B) Converting JavaScript objects into readable JSON format

C) Serializing objects for storage or transmission

D) Formatting JSON output with indentation

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22. Which of the following JSON values is equivalent to "no value"?

A) null

B) undefined

C) none

D) ""

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23. Which function can convert an API response from JSON to JavaScript objects?

A) JSON.stringify()

B) response.parse()

C) response.json()

D) JSON.decode()

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24. What is the purpose of the space parameter in JSON.stringify()?

A) To format the output with indentation

B) To compress the JSON output

C) To add extra spacing between keys and values

D) To add a specific number of spaces to the start of the output

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25. What is a common format for API error responses?

A) CSV file

B) JSON object

C) XML document

D) Plain text

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26. What does the package.json file in a Node.js project contain?

A) A list of all JavaScript files

B) The project's HTML templates

C) The project's CSS styles

D) Metadata about the project, dependencies, and scripts

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

A) It encrypts JSON payloads for secure transmission

B) It converts JSON to binary format

C) It compresses JSON data

D) It adds authentication to JSON

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

A) type: "email"

B) format: "email"

C) validate: "email"

D) pattern: "/[email]/"

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

A) ""

B) {}

C) null

D) []

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

A) The HTTP method to be used

B) The status of the response

C) The size of the request body

D) The format of the data being sent or expected

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