JavaScript JSON and Structured Data Quiz

Review

1. Which is a JSON value?

   JSON supports a number such as 42, but not JavaScript-only values like undefined, BigInt, or functions.
2. What does JSON.parse do?

   JSON.parse converts valid JSON text into an ECMAScript language value.
3. What happens when JSON.parse receives malformed JSON?

   Malformed JSON causes JSON.parse to throw a SyntaxError.
4. What does JSON.stringify normally return for a serializable object?

   JSON.stringify returns JSON text as a String.
5. What happens to an undefined object property during JSON.stringify?

   Unsupported object property values such as undefined are omitted.
6. What happens to undefined inside an array during JSON.stringify?

   Unsupported values in arrays are represented as null.
7. What is the main concern with very large JSON integers in JavaScript?

   ECMAScript Number cannot exactly represent every integer beyond its safe integer range.
8. What can a JSON.stringify replacer function do?

   A replacer can transform values or return undefined to exclude object properties/array entries according to serialization rules.
9. What can a JSON.parse reviver do?

   A reviver transforms values during parsing and can return undefined to delete a property or array element.
10. What does toJSON provide?

    JSON.stringify uses an object’s toJSON method when present to obtain the value to serialize.
11. For duplicate object names in JSON.parse, what happens?

    Later duplicate names overwrite earlier values during JSON.parse.
12. Does valid JSON guarantee an application-specific shape?

    JSON validity and application-level validation are separate concerns.
13. What does a JSON round trip preserve?

    JSON is a data interchange format and does not preserve arbitrary JavaScript object identity or behavior.
14. What does the space argument of JSON.stringify control?

    The space argument requests indentation in the generated JSON text.
15. Which sequence models a normal JSON boundary?

    Serialization produces JSON text and parsing consumes JSON text.
16. Why is {name:"Ada"} not JSON text?

    JSON object member names are strings and therefore use double quotes.
17. What does JSON.isRawJSON(obj) determine?

    JSON.isRawJSON returns true when the object has the [[IsRawJSON]] internal slot.
18. What should JSON.isRawJSON(JSON.rawJSON("42")) return when both methods are available?

    JSON.rawJSON creates the special raw-JSON object recognized by JSON.isRawJSON.
19. Is JSON.isRawJSON a general JSON validator?

    It is a narrow predicate for the special raw-JSON object, not a general JSON-text or schema validator.
20. What can distinguish a raw-JSON object from an ordinary lookalike with a rawJSON property?

    The specification identifies raw-JSON objects using the [[IsRawJSON]] internal slot.