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. How do you check if a string is valid JSON in JavaScript?

A) Use typeof to check its type

B) Use JSON.isValid()

C) Use JSON.check()

D) Parse it with JSON.parse() inside a try...catch block

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

A) JSON.debug()

B) JSON.parse()

C) JSON.stringify()

D) JSON.minify()

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

A) null

B) A key-value pair object

C) ReferenceError

D) SyntaxError: Unexpected identifier

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

A) format: "email"

B) type: "email"

C) validate: "email"

D) pattern: "/[email]/"

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5. What is the MIME type for JSON?

A) text/json

B) text/plain

C) application/javascript

D) application/json

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6. How does Elasticsearch use JSON?

A) To store and query documents

B) To validate user input

C) To define relational tables

D) To render dashboards

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7. What is the difference between allOf and oneOf in JSON Schema?

A) allOf validates all schemas, oneOf validates only one schema

B) oneOf requires at least one match, allOf requires none

C) allOf is for strings, oneOf is for arrays

D) allOf allows duplicates, oneOf does not

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8. Which of the following formats can JSON be easily converted into for data visualization?

A) All of the above

B) HTML

C) XML

D) CSV

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9. What is the purpose of JSON in REST APIs?

A) To define API endpoints

B) To render HTML pages

C) To structure and exchange data between client and server

D) To validate API responses

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10. Which keyword restricts the number of items in a JSON array?

A) maxItems

B) maxSize

C) arrayLimit

D) minLength

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11. What is the default value of additionalProperties in JSON Schema?

A) true

B) undefined

C) null

D) false

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12. Which of the following is a commonly used library for making API requests in JavaScript?

A) jQuery

B) D3.js

C) Lodash

D) Axios

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13. What is the result of trying to access a non-existent key in a JSON object?

A) Throws an error

B) Returns null

C) Returns undefined

D) Returns an empty string

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14. Can JSON objects contain duplicate keys?

A) Yes, with an error

B) Yes, but only for strings

C) No

D) Yes, the last key-value pair overrides the previous ones

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15. How are elements in a JSON array separated?

A) Colons

B) Semicolons

C) Commas

D) Dots

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16. What happens when you use JSON.stringify() on an object with a circular reference?

A) It converts the object to a string successfully

B) It throws a syntax error

C) It ignores the circular reference

D) It throws a TypeError

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

A) Validates against one specific type

B) Requires all listed schemas to match

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

D) Combines multiple schemas

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18. Which of the following is an invalid JSON structure?

A) { "key": "value", "key": "anotherValue" }

B) { "key": [1, 2, { "nested": "value" }] }

C) { "key": { "nested": { "deep": [1, 2] } } }

D) [ { "key1": "value1" }, { "key2": "value2" } ]

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

A) The special characters are escaped automatically

B) The key must be enclosed in double quotes

C) The key is ignored

D) It throws an error

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20. What is the most efficient way to handle large JSON datasets in memory-constrained environments?

A) Load the entire JSON at once

B) Use streaming APIs to process JSON incrementally

C) Convert JSON to XML first

D) Remove all nested objects

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21. Which of the following is used to validate the syntax of JSON data?

A) JSON Validator

B) JSON Compressor

C) JSON Formatter

D) JSON Beautifier

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22. Which tool is used to validate JSON syntax?

A) Postman

B) JSONLint

C) XMLParser

D) JSONParser

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23. What is the output of JSON.stringify() on a nested object?

A) A string representation of the nested object

B) A flattened version of the object

C) A deep copy of the object

D) Throws an error

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

A) name

B) "_name"

C) "name!"

D) "123name"

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

A) {}

B) ""

C) null

D) []

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

A) Using the JSON.validate() method

B) Checking the JSON string with isValid()

C) JSON parsing cannot produce errors

D) Using a try...catch block

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27. How do you specify that a JSON object must have at least one key in JSON Schema?

A) minItems: 1

B) minKeys: 1

C) minProperties: 1

D) required: true

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28. Which HTTP method is typically used for sending data to an API?

A) GET

B) DELETE

C) OPTIONS

D) POST

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29. What does the .eslintrc.json file configure in JavaScript projects?

A) Linting rules and code quality settings

B) Server configurations

C) Database schemas

D) Project dependencies

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

A) An array of types

B) A numeric range

C) A boolean flag

D) A single string

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