🧾 JSON Basic Syntax Rules – A Simple Guide for Beginners (2025)
🧲 Introduction – Why Syntax Rules Matter in JSON
JSON (JavaScript Object Notation) is known for being clean, consistent, and easy to read. But like any structured format, it has strict syntax rules you must follow. Whether you’re writing API responses, saving configuration files, or exchanging data between systems, following JSON syntax correctly ensures your data is valid and parsable.
🎯 In this guide, you’ll learn:
- The core syntax rules of JSON
- How to format valid JSON objects and arrays
- What characters and structures are required
- Common mistakes to avoid
✅ Core JSON Syntax Rules
Below are the fundamental rules you must follow to create valid JSON data.
1️⃣ Data is in name/value pairs
- Each pair is written as:
"key": value - Keys must be strings in double quotes
✅ Example:
{ "name": "Alice" }
2️⃣ Data is separated by commas
- Multiple key/value pairs must be separated by commas
- No trailing comma after the last pair
✅ Example:
{
"name": "Alice",
"age": 25
}
3️⃣ Curly braces {} hold objects
- JSON objects use
{}to wrap key/value pairs
✅ Example:
{ "city": "New York" }
4️⃣ Square brackets [] hold arrays
- Arrays can contain values or multiple JSON objects
✅ Example:
[ "Apple", "Banana", "Cherry" ]
✅ Example with objects:
[
{ "name": "John" },
{ "name": "Jane" }
]
5️⃣ Keys must be strings in double quotes
- No single quotes, no unquoted keys
❌ Invalid:
{ name: 'John' }
✅ Valid:
{ "name": "John" }
6️⃣ Values must be one of the following types:
String(in double quotes)Number(no quotes)Object(JSON object)Array(JSON array)Boolean(trueorfalse)null
🚫 Common Syntax Mistakes to Avoid
| ❌ Mistake | 💥 Error Message / Problem |
|---|---|
| Using single quotes | JSON only accepts double quotes for strings |
| Trailing comma in objects/arrays | Causes a parser error |
| Unquoted keys | All keys must be in double quotes |
| Including functions or comments | Not allowed in standard JSON |
| Using undefined values | JSON doesn’t support undefined |
🧪 Invalid JSON (Example)
{
name: 'Alice', // ❌ wrong quotes, unquoted key, and comment
}
✅ Corrected JSON
{
"name": "Alice"
}
📌 Summary – Recap & Next Steps
Following JSON syntax ensures your data is machine-readable and web-compatible. Small mistakes—like a missing quote or trailing comma—can break an entire API response.
🔍 Key Takeaways:
- Keys must be strings in double quotes
- Use commas to separate pairs or items
- Always use curly braces
{}for objects and square brackets[]for arrays - JSON does not allow comments, functions, or trailing commas
⚙️ Real-world use:
Strict adherence to JSON syntax is required when working with REST APIs, config files, AJAX requests, and tools like Postman, cURL, and Node.js.
❓ FAQ – JSON Syntax
❓ Can I use single quotes in JSON?
❌ No. JSON requires double quotes " " for strings and keys.
❓ Are comments allowed in JSON?
❌ No. JSON strictly forbids comments. You must remove them before parsing.
❓ Is a trailing comma allowed in a JSON array or object?
❌ No. JSON does not allow trailing commas after the last item.
❓ Can JSON store functions or undefined values?
❌ No. JSON is purely a data format and does not support functions or undefined.
❓ How can I check if my JSON is valid?
✅ Use online tools like jsonlint.com or run JSON.parse() in JavaScript to validate.
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