Top 100 JSON Interview Questions and Answers PDF Download

Top 100 JSON Interview Questions and Answers

1. What is JSON?

   JSON stands for JavaScript Object Notation. It is a lightweight data interchange format used to store and exchange data between systems and programs.

2. What are the basic data types supported by JSON?

   JSON supports the following basic data types: strings, numbers, booleans, null, arrays, and objects.

3. What is the syntax for writing a JSON object?

   A JSON object is written as a key-value pair, where keys are enclosed in double quotes and values can be any valid JSON data type. For example: { "name": "John", "age": 30 }

4. How do you represent an array in JSON?

   An array in JSON is represented using square brackets, and elements are separated by commas. For example: [1, 2, 3]

5. Can you nest JSON objects?

   Yes, JSON objects can be nested. An object can contain another object as its value. For example: { "person": { "name": "Alice", "age": 25 } }

6. How do you represent a string in JSON?

   A string in JSON is represented by enclosing the text in double quotes. For example: "Hello, World!"

7. What is the purpose of JSON.stringify() in JavaScript?

   JSON.stringify() is used to convert a JavaScript object or value to a JSON string representation.

8. What is the purpose of JSON.parse() in JavaScript?

   JSON.parse() is used to parse a JSON string and convert it back to a JavaScript object or value.

9. How do you handle comments in JSON?

   JSON does not support comments. Any comment within JSON data will result in a syntax error.

10. Can you use single quotes for strings in JSON?

    No, JSON only allows double quotes for representing strings. Using single quotes will result in a syntax error.

11. What is the difference between JSON and JavaScript object literal notation?

    JSON and JavaScript object literal notation are similar, but there are some differences. In JSON, keys must be enclosed in double quotes, while in JavaScript object literal notation, quotes are optional for keys. JSON doesn't support functions, while JavaScript object literal notation allows functions as values.

12. Can you have a trailing comma in a JSON object or array?

    No, JSON does not allow trailing commas. Adding a trailing comma will result in a syntax error.

13. How do you represent a date in JSON?

    JSON does not have a built-in date type. Dates are typically represented as strings in a specific format (e.g., "YYYY-MM-DD").

14. What is the significance of the Content-Type header when working with JSON?

    The Content-Type header is essential when sending JSON data over the network. It should be set to "application/json" to indicate that the data being sent or received is in JSON format.

15. What is JSONP (JSON with Padding)?

    JSONP is a technique used to overcome the same-origin policy limitations when making cross-domain AJAX requests. It involves wrapping the JSON response in a callback function and using a script tag to load the data dynamically.

16. How do you handle circular references in JSON objects?

    JSON.stringify() will throw an error if it encounters a circular reference in the object. To handle circular references, you need to use a third-party library or manually break the circular reference before calling JSON.stringify().

17. What is the maximum size of JSON data that can be processed by most browsers?

    Most browsers have a limit on the size of JSON data that can be processed, typically ranging from a few MBs to tens of MBs. Exceeding this limit can lead to memory and performance issues.

18. What is JSON Schema?

    JSON Schema is a vocabulary used to validate JSON data against a specific schema. It defines the data types, structure, and constraints that a JSON object should follow.

19. How do you handle errors when parsing JSON?

    When parsing JSON using JSON.parse(), you should wrap it in a try-catch block to handle any syntax errors or exceptions that may occur.

20. Is the order of elements guaranteed in a JSON object?

    No, the order of elements in a JSON object is not guaranteed. JSON is designed to be a data interchange format and does not preserve the order of object keys.

21. How do you remove an element from a JSON object?

    To remove an element from a JSON object, you can use the delete operator in JavaScript. For example: delete jsonObject.keyToRemove;

22. Can JSON have duplicate keys in an object?

    No, JSON does not allow duplicate keys in an object. If duplicate keys are present, the last occurrence will overwrite the earlier ones.

23. What is JSON-B (JSON Binding)?

    JSON-B is a standard Java API for binding JSON data to Java objects and vice versa. It provides annotations and APIs to customize the mapping between JSON and Java objects.

24. How do you access nested values in a JSON object?

    You can access nested values in a JSON object by chaining the keys together. For example: jsonObject.key1.key2;

25. What is JSON Web Token (JWT)?

    JSON Web Token (JWT) is a compact and self-contained way of representing information between two parties. It is used for securely transmitting information as a JSON object.

26. Can JSON have multiple lines?

    No, JSON should be a single-line string. If you need to include line breaks, you can use the escape sequence \n to represent a newline character.

27. How do you handle special characters in JSON strings?

    You can use escape sequences to handle special characters in JSON strings. For example: \" for double quote, \\ for backslash, \b for backspace, \f for form feed, \n for newline, \r for carriage return, and \t for horizontal tab.

28. What is JSON-RPC?

    JSON-RPC is a remote procedure call (RPC) protocol encoded in JSON. It enables you to make remote procedure calls over HTTP or other transport protocols using JSON as the data format.

29. What is the difference between JSON and XML?

    JSON and XML are both used for data interchange, but they have some differences. JSON is more lightweight and easier to parse in JavaScript, while XML is more suitable for document-oriented data. JSON uses a simpler syntax compared to XML's verbose structure.

30. How do you handle null values in JSON?

    In JSON, a null value is represented as the keyword null without quotes. For example: { "name": null }

31. Can JSON contain functions as values?

    No, JSON does not support functions as values. If you need to represent executable code, you may use other formats like JavaScript or use a string to hold the function and later eval() it.

32. What is the role of JSON in AJAX?

    In AJAX (Asynchronous JavaScript and XML), JSON is commonly used as the data format for exchanging information between the client and server. JSON's lightweight nature makes it more efficient for data transfer over XML.

33. How do you handle trailing whitespaces in JSON?

    JSON ignores trailing whitespaces, so it won't affect the parsing or data itself. However, it's considered a best practice to remove unnecessary whitespaces when transmitting JSON data over the network to reduce file size.

34. What is JSON Merge Patch?

    JSON Merge Patch is a format for describing changes to a JSON document. It allows you to update an existing JSON document by sending only the changes rather than the whole document.

35. How do you escape a JSON string in JavaScript?

    You can use the JSON.stringify() method to escape a JSON string in JavaScript. This method will escape any special characters and ensure the string is correctly formatted as a JSON value.

36. What is JSONP (JSON with Padding) and how does it work?

    JSONP is a workaround to make cross-origin requests in browsers that do not support CORS (Cross-Origin Resource Sharing). It involves adding a script tag to the DOM with a src attribute pointing to a JSON file hosted on a different domain. The server responds with a JSON file wrapped in a function call specified in the callback parameter of the request. When the script is loaded, the specified function is executed, and the JSON data is passed as an argument to the function, enabling the client-side code to access the JSON data.

37. How can you prevent JSON injection?

    To prevent JSON injection, you should always validate and sanitize user input before generating JSON data. Avoid evaluating JSON data as executable code, especially if it originates from untrusted sources.

38. What is the use of JSON in JavaScript?

    JSON plays a crucial role in JavaScript as a data interchange format. It allows JavaScript to exchange data with servers, making it an essential component of AJAX applications. JSON is also used for configuration files, storing application data, and representing structured data in modern web development.

39. What is the MIME type for JSON?

    The MIME type for JSON is "application/json". It is used in HTTP headers to indicate that the content being transferred is in JSON format.

40. How do you pretty-print JSON data?

    You can use the JSON.stringify() method with the third parameter as the number of spaces you want to use for indentation. For example: JSON.stringify(jsonObject, null, 2) will produce a pretty-printed JSON string with an indentation of 2 spaces.

41. What is the JSON syntax for an empty object?

    An empty object in JSON is represented by two curly brackets with no key-value pairs inside. For example: {}

42. How do you escape a JSON string in PHP?

    In PHP, you can use the json_encode() function to escape a JSON string. This function will encode any special characters and ensure the string is correctly formatted as a JSON value.

43. What is the difference between JSON and BSON?

    JSON (JavaScript Object Notation) is a human-readable data interchange format, while BSON (Binary JSON) is a binary representation of JSON. BSON is designed to be more efficient in storage and parsing, making it suitable for high-performance applications.

44. How do you convert a JSON string to a JavaScript object?

    You can use the JSON.parse() method in JavaScript to convert a JSON string to a JavaScript object. For example: var jsonObject = JSON.parse(jsonString);

45. What is the JSONP callback function name?

    The JSONP callback function name is specified by the client-side code making the JSONP request. It is usually provided as a query parameter in the request URL, and the server responds with the JSON data wrapped inside a function call with the specified name.

46. What is JSON-RPC?

    JSON-RPC is a remote procedure call (RPC) protocol encoded in JSON. It allows you to make remote procedure calls over HTTP or other transport protocols using JSON as the data format.

47. How do you create an empty JSON object in Python?

    In Python, you can create an empty JSON object using an empty dictionary {}. For example: jsonObject = {}

48. What is the JSON syntax for an empty array?

    An empty array in JSON is represented by two square brackets with no elements inside. For example: []

49. How do you include a JSON file in an HTML page?

    You can include a JSON file in an HTML page using a script tag with the src attribute pointing to the URL of the JSON file. For example:

50. What is JSON-P?

    JSON-P (JSON with Padding) is a technique used to overcome the same-origin policy limitations when making cross-domain AJAX requests. It involves wrapping the JSON response in a dynamically created script tag and using a callback function to process the data.

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

    You can check if a string is a valid JSON using a try-catch block when parsing the JSON with JSON.parse(). If the parsing succeeds without any errors, the string is valid JSON.

52. What is the difference between JSON and YAML?

    JSON and YAML are both data interchange formats, but they have some differences. JSON is simpler and more lightweight, while YAML is more human-readable and supports comments and complex data structures.

53. How do you create a JSON array in Java?

    In Java, you can create a JSON array using the JSONArray class from the JSON library of your choice (e.g., org.json.JSONArray, com.fasterxml.jackson.databind.JsonNode, or org.json.simple.JSONArray).

54. What is the JSON-RPC request format?

    The JSON-RPC request format is a JSON object with the following required properties: "jsonrpc" (a string specifying the JSON-RPC version), "method" (a string specifying the name of the method to be called), and "params" (an array or object containing the method parameters).

55. How do you include a JSON file in a JavaScript file?

    You can include a JSON file in a JavaScript file by making an AJAX request to the JSON file's URL using technologies like XMLHttpRequest or fetch API. Alternatively, you can load the JSON file using server-side code and embed the JSON data directly into the JavaScript file.

56. What is the JSON-RPC response format?

    The JSON-RPC response format is a JSON object with the following required properties: "jsonrpc" (a string specifying the JSON-RPC version), "result" (the result of the method call), and "id" (a unique identifier matching the ID of the corresponding request).

57. How do you handle large JSON files in Python?

    To handle large JSON files in Python, you can read and process the file in chunks instead of loading the entire file into memory at once. You can use libraries like ijson or jsonlines that allow you to read JSON data incrementally.

58. What is JSON-PHP?

    JSON-PHP is not a specific technology or library. It is a term used to describe the process of working with JSON data in PHP, which includes functions like json_encode() and json_decode() for handling JSON data in PHP applications.

59. What is the JSON-RPC batch request?

    The JSON-RPC batch request is an array of JSON-RPC requests sent to the server in a single HTTP request. Each individual request in the batch is a JSON object containing the required properties (e.g., "jsonrpc", "method", "params") for that particular request.

60. What is JSON-RPC 2.0?

    JSON-RPC 2.0 is a revision of the JSON-RPC specification that addresses some shortcomings of the original JSON-RPC 1.0. It is more strict in its error handling, uses JSON objects instead of arrays for method parameters, and introduces the concept of batch requests.

61. How do you pretty-print JSON data in Python?

    You can use the json.dumps() method with the indent parameter to pretty-print JSON data in Python. For example: json.dumps(jsonObject, indent=4)

62. What is JSON streaming?

    JSON streaming is a technique used to process large JSON datasets without loading the entire JSON data into memory. It involves reading and parsing the JSON data incrementally as it is being transmitted over the network or read from a file.

63. What is the JSON-RPC notification?

    The JSON-RPC notification is a request that does not expect a response from the server. It is similar to a regular JSON-RPC request but does not include the "id" property, and the server is not required to send a response.

64. What is JSON Pointer?

    JSON Pointer is a string syntax used to identify a specific value within a JSON document. It uses a sequence of slash-separated tokens to navigate through the JSON structure and access the desired value.

65. How do you encode JSON in PHP?

    You can encode JSON in PHP using the json_encode() function. This function converts a PHP value (arrays or objects) into a JSON-encoded string.

66. What is JSON-B (JSON Binding) in Java?

    JSON-B (JSON Binding) is a standard Java API for binding JSON data to Java objects and vice versa. It provides annotations and APIs to customize the mapping between JSON and Java objects.

67. How do you decode JSON in PHP?

    You can decode JSON in PHP using the json_decode() function. This function converts a JSON-encoded string into a PHP value (arrays or objects).

68. What is JSON Web Token (JWT)?

    JSON Web Token (JWT) is a compact and self-contained way of representing information between two parties. It is used for securely transmitting information as a JSON object.

69. How do you validate JSON data in Python?

    You can validate JSON data in Python using JSON Schema validation libraries like jsonschema. These libraries allow you to define a JSON Schema that specifies the structure and constraints of the JSON data, and then validate the data against that schema.

70. What is JSONP (JSON with Padding)?

    JSONP is a technique used to overcome the same-origin policy limitations when making cross-domain AJAX requests. It involves wrapping the JSON response in a callback function and using a script tag to load the data dynamically.

71. How do you handle circular references in JSON objects?

    JSON.stringify() will throw an error if it encounters a circular reference in the object. To handle circular references, you need to use a third-party library or manually break the circular reference before calling JSON.stringify().

72. What is the maximum size of JSON data that can be processed by most browsers?

    Most browsers have a limit on the size of JSON data that can be processed, typically ranging from a few MBs to tens of MBs. Exceeding this limit can lead to memory and performance issues.

73. What is JSON Schema?

    JSON Schema is a vocabulary used to validate JSON data against a specific schema. It defines the data types, structure, and constraints that a JSON object should follow.

74. How do you handle errors when parsing JSON?

    When parsing JSON using JSON.parse(), you should wrap it in a try-catch block to handle any syntax errors or exceptions that may occur.

75. Is the order of elements guaranteed in a JSON object?

    No, the order of elements in a JSON object is not guaranteed. JSON is designed to be a data interchange format and does not preserve the order of object keys.

76. How do you remove an element from a JSON object?

    To remove an element from a JSON object, you can use the delete operator in JavaScript. For example: delete jsonObject.keyToRemove;

77. Can JSON have duplicate keys in an object?

    No, JSON does not allow duplicate keys in an object. If duplicate keys are present, the last occurrence will overwrite the earlier ones.

78. What is JSON-B (JSON Binding)?

    JSON-B is a standard Java API for binding JSON data to Java objects and vice versa. It provides annotations and APIs to customize the mapping between JSON and Java objects.

79. How do you access nested values in a JSON object?

    You can access nested values in a JSON object by chaining the keys together. For example: jsonObject.key1.key2;

80. What is JSON Web Token (JWT)?

    JSON Web Token (JWT) is a compact and self-contained way of representing information between two parties. It is used for securely transmitting information as a JSON object.

81. Can JSON have multiple lines?

    No, JSON should be a single-line string. If you need to include line breaks, you can use the escape sequence \n to represent a newline character.

82. How do you handle special characters in JSON strings?

    You can use escape sequences to handle special characters in JSON strings. For example: \" for double quote, \\ for backslash, \b for backspace, \f for form feed, \n for newline, \r for carriage return, and \t for horizontal tab.

83. What is JSON-RPC?

    JSON-RPC is a remote procedure call (RPC) protocol encoded in JSON. It enables you to make remote procedure calls over HTTP or other transport protocols using JSON as the data format.

84. What is the difference between JSON and XML?

    JSON and XML are both used for data interchange, but they have some differences. JSON is more lightweight and easier to parse in JavaScript, while XML is more suitable for document-oriented data. JSON uses a simpler syntax compared to XML's verbose structure.

85. How do you handle null values in JSON?

    In JSON, a null value is represented as the keyword null without quotes. For example: { "name": null }

86. Can JSON contain functions as values?

    No, JSON does not support functions as values. If you need to represent executable code, you may use other formats like JavaScript or use a string to hold the function and later eval() it.

87. What is the role of JSON in AJAX?

    In AJAX (Asynchronous JavaScript and XML), JSON is commonly used as the data format for exchanging information between the client and server. JSON's lightweight nature makes it more efficient for data transfer over XML.

88. How do you handle trailing whitespaces in JSON?

    JSON ignores trailing whitespaces, so it won't affect the parsing or data itself. However, it's considered a best practice to remove unnecessary whitespaces when transmitting JSON data over the network to reduce file size.

89. What is JSON Merge Patch?

    JSON Merge Patch is a format for describing changes to a JSON document. It allows you to update an existing JSON document by sending only the changes rather than the whole document.

90. How do you escape a JSON string in JavaScript?

    You can use the JSON.stringify() method to escape a JSON string in JavaScript. This method will escape any special characters and ensure the string is correctly formatted as a JSON value.

91. What is JSONP (JSON with Padding) and how does it work?

    JSONP is a workaround to make cross-origin requests in browsers that do not support CORS (Cross-Origin Resource Sharing). It involves adding a script tag to the DOM with a src attribute pointing to a JSON file hosted on a different domain. The server responds with a JSON file wrapped in a function call specified in the callback parameter of the request. When the script is loaded, the specified function is executed, and the JSON data is passed as an argument to the function, enabling the client-side code to access the JSON data.

92. How can you prevent JSON injection?

    To prevent JSON injection, you should always validate and sanitize user input before generating JSON data. Avoid evaluating JSON data as executable code, especially if it originates from untrusted sources.

93. What is the use of JSON in JavaScript?

    JSON plays a crucial role in JavaScript as a data interchange format. It allows JavaScript to exchange data with servers, making it an essential component of AJAX applications. JSON is also used for configuration files, storing application data, and representing structured data in modern web development.

94. What is the MIME type for JSON?

    The MIME type for JSON is "application/json". It is used in HTTP headers to indicate that the content being transferred is in JSON format.

95. How do you pretty-print JSON data?

    You can use the JSON.stringify() method with the third parameter as the number of spaces you want to use for indentation. For example: JSON.stringify(jsonObject, null, 2) will produce a pretty-printed JSON string with an indentation of 2 spaces.

96. What is the JSON syntax for an empty object?

    An empty object in JSON is represented by two curly brackets with no key-value pairs inside. For example: {}

97. How do you escape a JSON string in PHP?

    In PHP, you can use the json_encode() function to escape a JSON string. This function will encode any special characters and ensure the string is correctly formatted as a JSON value.

98. What is the difference between JSON and BSON?

    JSON (JavaScript Object Notation) is a human-readable data interchange format, while BSON (Binary JSON) is a binary representation of JSON. BSON is designed to be more efficient in storage and parsing, making it suitable for high-performance applications.

99. How do you convert a JSON string to a JavaScript object?

    You can use the JSON.parse() method in JavaScript to convert a JSON string to a JavaScript object. For example: var jsonObject = JSON.parse(jsonString);

100. What is the JSONP callback function name?

     The JSONP callback function name is specified by the client-side code making the JSONP request. It is usually provided as a query parameter in the request URL, and the server responds with the JSON data wrapped inside a function call with the specified name.

101. What is JSON-RPC?

     JSON-RPC is a remote procedure call (RPC) protocol encoded in JSON. It allows you to make remote procedure calls over HTTP or other transport protocols using JSON as the data format.

102. How do you create an empty JSON object in Python?

     In Python, you can create an empty JSON object using an empty dictionary {}. For example: jsonObject = {}

103. What is the JSON syntax for an empty array?

     An empty array in JSON is represented by two square brackets with no elements inside. For example: []

104. How do you include a JSON file in an HTML page?

     You can include a JSON file in an HTML page using a script tag with the src attribute pointing to the URL of the JSON file. For example:

105. What is JSON-P?

     JSON-P (JSON with Padding) is a technique used to overcome the same-origin policy limitations when making cross-domain AJAX requests. It involves wrapping the JSON response in a dynamically created script tag and using a callback function to process the data.

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

     You can check if a string is a valid JSON using a try-catch block when parsing the JSON with JSON.parse(). If the parsing succeeds without any errors, the string is valid JSON.

107. What is the difference between JSON and YAML?

     JSON and YAML are both data interchange formats, but they have some differences. JSON is simpler and more lightweight, while YAML is more human-readable and supports comments and complex data structures.

108. How do you create a JSON array in Java?

     In Java, you can create a JSON array using the JSONArray class from the JSON library of your choice (e.g., org.json.JSONArray, com.fasterxml.jackson.databind.JsonNode, or org.json.simple.JSONArray).

109. What is the JSON-RPC request format?

     The JSON-RPC request format is a JSON object with the following required properties: "jsonrpc" (a string specifying the JSON-RPC version), "method" (a string specifying the name of the method to be called), and "params" (an array or object containing the method parameters).

110. How do you include a JSON file in a JavaScript file?

     You can include a JSON file in a JavaScript file by making an AJAX request to the JSON file's URL using technologies like XMLHttpRequest or fetch API. Alternatively, you can load the JSON file using server-side code and embed the JSON data directly into the JavaScript file.

111. What is the JSON-RPC response format?

     The JSON-RPC response format is a JSON object with the following required properties: "jsonrpc" (a string specifying the JSON-RPC version), "result" (the result of the method call), and "id" (a unique identifier matching the ID of the corresponding request).

112. How do you handle large JSON files in Python?

     To handle large JSON files in Python, you can read and process the file in chunks instead of loading the entire file into memory at once. You can use libraries like ijson or jsonlines that allow you to read JSON data incrementally.

113. What is JSON-PHP?

     JSON-PHP is not a specific technology or library. It is a term used to describe the process of working with JSON data in PHP, which includes functions like json_encode() and json_decode() for handling JSON data in PHP applications.

114. What is the JSON-RPC batch request?

     The JSON-RPC batch request is an array of JSON-RPC requests sent to the server in a single HTTP request. Each individual request in the batch is a JSON object containing the required properties (e.g., "jsonrpc", "method", "params") for that particular request.

115. What is JSON-RPC 2.0?

     JSON-RPC 2.0 is a revision of the JSON-RPC specification that addresses some shortcomings of the original JSON-RPC 1.0. It is more strict in its error handling, uses JSON objects instead of arrays for method parameters, and introduces the concept of batch requests.

116. How do you pretty-print JSON data in Python?

     You can use the json.dumps() method with the indent parameter to pretty-print JSON data in Python. For example: json.dumps(jsonObject, indent=4)

117. What is JSON streaming?

     JSON streaming is a technique used to process large JSON datasets without loading the entire JSON data into memory. It involves reading and parsing the JSON data incrementally as it is being transmitted over the network or read from a file.

118. What is the JSON-RPC notification?

     The JSON-RPC notification is a request that does not expect a response from the server. It is similar to a regular JSON-RPC request but does not include the "id" property, and the server is not required to send a response.

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