JSON Data Types — Interview Questions
⚡ Short Answer
JSON supports six value types: string (double-quoted), number, boolean (true/false), null, object ({}), and array ([]). It has no date, integer-vs-float distinction, undefined, function, or comment types — dates are usually sent as ISO-8601 strings and big/precise numbers as strings.
☕Coffee Chat Question
Concept Made Simple
“What data types does JSON support?”
🧠Mind Map Answer
Remember It Faster
⌨️Hands-on Keyboard
Learn by Doing
{
"name": "Guru",
"age": 30,
"verified": true,
"manager": null,
"skills": ["Java", "AWS"],
"joined": "2026-08-01T09:00:00Z"
}🔥What If?
Think Beyond the Expected
How do you represent a date, since JSON has no date type?
Use a string, almost always ISO-8601 ("2026-08-01T09:00:00Z"), and parse it on each side (new Date(str) in JS, java.time.Instant in Java). Some teams send a Unix epoch number instead. There's no native date, so both parties must agree on the string/number convention.
😂Real World
The 'JSON has no date' fact bites everyone eventually — you JSON.stringify a Date and it becomes an ISO string, then forget to parse it back and end up comparing a string to a Date. Money and IDs are often sent as strings to avoid float precision loss.
🎯Interviewer's Expectation
Keywords they're listening for:
⚠️Common Mistakes
- ✗Expecting a native date type
- ✗Using single quotes for strings
- ✗Assuming numbers keep exact precision (float issues)
✅Best Practices
- ✓Send dates as ISO-8601 strings
- ✓Send money/large IDs as strings to avoid float errors
- ✓Distinguish null (known-empty) from a missing key
🔁Follow-up Questions
- 1Why send large numbers or money as strings?
- 2How is null different from an absent key?
- 3What happens to undefined during JSON.stringify?
🧩Related Technologies
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Plain-language foundations
I'm preparing for a software engineering interview and want to understand this from scratch, as a beginner. Topic: Syntax (JSON) Interview question: "What data types does JSON support?" Please: 1. Explain the core idea in simple, plain language, using an everyday analogy. 2. Define any technical terms you use. 3. Walk through one small, concrete example. 4. Finish with a single sentence I can easily remember. Keep the tone friendly and assume I'm new to this topic.
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