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.

1 / 30

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

A) Serializing objects for storage or transmission

B) Formatting JSON output with indentation

C) Converting JavaScript objects into readable JSON format

D) Serializing objects with circular references

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2. Which keyword defines a numeric range in JSON Schema?

A) min and max

B) minimum and maximum

C) range

D) numberRange

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3. Which of the following files often uses JSON for configuration?

A) preferences.ini

B) config.txt

C) config.xml

D) settings.json

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4. 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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5. Which of the following is valid JSON for a mixed data type array?

A) [ "Alice", "25", true ]

B) [ { "name": "Alice" }, 25, "true" ]

C) [ "Alice", 25, true ]

D) All of the above

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

A) "null"

B) (null)

C) null

D) NULL

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7. 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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8. Which of the following is NOT valid in JSON?

A) Strings

B) Comments

C) Numbers

D) Boolean values

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9. Which of the following data types can JSON arrays contain?

A) Only strings

B) Only numbers

C) Only objects

D) Mixed data types

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10. Which of the following is a common use of JSON in web development?

A) Defining CSS styles

B) Compiling JavaScript code

C) Storing and exchanging data between client and server

D) Rendering HTML elements

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11. What happens when you pass a replacer function to JSON.stringify()?

A) Throws an error if the function is invalid

B) It filters the properties to be included in the JSON string

C) It validates the JSON string

D) It ensures all properties are stringified

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12. Which of the following is NOT a valid JSON key?

A) "123name"

B) name

C) "name!"

D) "_name"

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

A) The key is ignored

B) It throws an error

C) The key must be enclosed in double quotes

D) The special characters are escaped automatically

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14. What symbol is used to enclose a JSON array?

A) {}

B) ()

C) <>

D) []

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15. What is a safe alternative to eval() for parsing JSON in JavaScript?

A) JSON.stringify()

B) JSON.parse()

C) JSON.minify()

D) JSON.debug()

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

A) Returns undefined

B) Continues execution without errors

C) Throws a TypeError

D) Returns an empty object

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

A) Defines the keys allowed in an object

B) Defines the maximum number of keys in an object

C) Specifies the data type of an array

D) Lists all required fields in an object

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18. What does the JSON.parse() method do in JavaScript?

A) Converts a JSON string into a JavaScript object

B) Parses a JSON string into an XML object

C) Validates a JSON string

D) Converts a JavaScript object into a JSON string

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19. What happens if there is a syntax error in a JSON file?

A) It will fail to parse

B) It gets ignored

C) The JSON file still works

D) It displays a warning but continues

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20. Which tool can be used to measure JSON parsing performance in JavaScript?

A) JSON Formatter

B) Chrome DevTools

C) JSON Schema Validator

D) JSONLint

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

A) window.debug()

B) console.parse()

C) JSON.log()

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

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22. Which of these is a valid JSON object?

A) [name: "John", age: 30]

B) {name = "John"; age = 30}

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

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

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23. Which type of JSON structure is most efficient for transmitting data?

A) JSON with comments

B) Flat, simple key-value pairs

C) Deeply nested objects

D) Objects with arrays

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24. What is the maximum depth for nesting in JSON?

A) Unlimited

B) 10 levels

C) 5 levels

D) Depends on the programming language and environment

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25. How do you merge two JSON objects?

A) Use JSON.stringify()

B) Use array.push()

C) Use JSON.merge()

D) Use Object.assign()

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26. Which of these is NOT a valid JSON value?

A) A null value

B) A function

C) A string

D) A boolean

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

A) JSON Injection

B) JSON Flooding

C) JSON Parsing Loops

D) JSON Brute Force

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

A) SyntaxError: Unexpected identifier

B) A key-value pair object

C) null

D) ReferenceError

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29. Can a JSON object be empty?

A) Yes

B) No

C) Only when nested

D) Only in arrays

30 / 30

30. What happens if a JSON object has circular references when using JSON.stringify()?

A) It returns an empty object

B) It skips the circular reference and continues

C) It throws a TypeError

D) It converts successfully

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