Complete Guide to JSON Parsing, Schema Validation, and Error Handling.

1. The Universality of JSON in Modern Systems

JavaScript Object Notation (JSON), standardized under RFC 8259 and ECMA-404, has become the undisputed lingua franca of data interchange across the internet. From REST APIs and GraphQL payloads to NoSQL database documents and configuration files, JSON's language-agnostic text format balances human readability with machine parseability.

However, beneath its seemingly simple grammar consisting of objects, arrays, strings, numbers, booleans, and null, lies a variety of edge cases that can compromise application reliability and security. Understanding how parsers interpret bytes, how validators verify constraints, and how serialization pitfalls occur is essential for robust engineering.

2. Core Grammar and Strict Serialization Rules

Unlike JavaScript object literals, JSON enforces strict syntactic constraints. Many developers accidentally write malformed JSON by relying on permissive language features:

• Mandatory Double Quotes: Keys and string values must always be enclosed in double quotes ("key": "value"). Single quotes ('key') or unquoted keys are invalid syntax.
• No Trailing Commas: Commas must separate elements, but a trailing comma after the final array item or object key-value pair will trigger syntax errors in standard parsers.
• Prohibited Number Formats: Leading zeros (e.g., 0123), hexadecimal literals (0xFF), and values like NaN or Infinity are explicitly forbidden. Numbers must follow standard decimal representation.
• No Native Comments: The JSON specification does not support single-line (//) or multi-line (/* */) comments.

{
  name: 'Telemetry',
  retries: 3, // retry count
  timeout: Infinity,
}

{
  "name": "Telemetry",
  "retries": 3,
  "timeout": null
}