Working with Comments in JSON5-Compatible Formatters

JSON (JavaScript Object Notation) is a lightweight data-interchange format widely used across the web. However, one common complaint about standard JSON is its lack of support for comments. This limitation can make configuration files or complex data structures harder to understand without external documentation.

JSON5 is an extension of JSON that aims to make it easier for humans to write and maintain, while still being a subset of ECMAScript 5 (like JSON). One of its most popular features is the ability to include comments. This guide explores how to work with comments in JSON5 and why it's a valuable feature.

Why Standard JSON Doesn't Allow Comments

The original JSON specification deliberately omitted comments. Douglas Crockford, the creator of JSON, stated that he removed comments because he saw people using them to include parsing directives. His goal was to keep JSON purely a data format, free from implementation details or instructions within the data itself. While this decision keeps JSON simple and focused, it removes a useful feature for human readability and maintainability, especially for configuration files.

JSON5: JSON for Humans

JSON5 extends JSON with several features aimed at improving human readability. These include:

• Comments (single-line and multi-line)
• Trailing commas in objects and arrays
• Unquoted object keys (if they are valid identifiers)
• Single-quoted strings
• Multiline strings
• Reserved words as keys
• Other number formats (hexadecimal, positive/negative infinity, NaN)

Among these, the ability to add comments is arguably the most significant for documentation and clarity.

Adding Comments in JSON5

JSON5 supports two types of comments familiar from JavaScript and many other programming languages:

1. Single-Line Comments (`//`)

These comments start with two forward slashes (`//`) and continue to the end of the line. They are useful for adding brief explanations or notes next to specific properties or values.

{
  "database": {
    "host": "localhost", // Database server address
    "port": 5432,        // Port number for connection
    "username": "admin"
    // Note: Password should be stored securely, not here!
  },
  "api": {
    "timeout": 5000      // API request timeout in ms
  }
}

2. Multi-Line Comments (`/* */`)

These comments start with `/*` and end with `*/`. They can span multiple lines and are ideal for more detailed explanations, descriptions of sections, or temporarily commenting out blocks of code.

{
  /*
    Application Configuration File

    This file contains settings for database connections,
    API endpoints, feature flags, etc.
    Please be careful when modifying this file.
  */
  "appSettings": {
    "appName": "My Awesome App",
    "version": "1.0.0"
  },
  /*
  "featureFlags": {
    "beta": true, // Temporarily disabled for production testing
    "new_dashboard": false
  },
  */
  "logging": {
    "level": "info" // Set logging level (debug, info, warn, error)
  }
}

Benefits of Using Comments in JSON5

Adding comments to your JSON5 files offers several advantages:

• Improved Readability: Explain complex settings or data structures directly within the file.
• Easier Maintenance: Future users (including yourself) can quickly understand the purpose of different parts of the configuration or data.
• Self-Documenting: The file becomes its own documentation, reducing the need for separate documents (though complex systems may still require them).
• Temporary Disabling: Easily comment out configuration options or data entries without deleting them.

Using JSON5-Compatible Formatters and Parsers

To work with JSON5 files, you need tools that understand the JSON5 specification. Standard JSON parsers will throw errors when encountering comments or other JSON5 features.

Look for text editors, IDEs, and online formatters/validators that explicitly state support for JSON5. These tools will correctly parse, format, and validate your JSON5 files, including preserving or handling comments as appropriate.

Tips for Effective Commenting in JSON5

• Be Concise: Comments should clarify, not clutter. Keep them brief and to the point.
• Explain the Why: Instead of just restating what the code does, explain *why* it does it or the purpose of a specific setting.
• Keep Them Updated: Outdated comments are misleading. Ensure comments are updated whenever the corresponding data changes.
• Use for Configuration: JSON5 is particularly useful for configuration files where human readability and notes are highly beneficial.
• Validate: Even with comments, always validate your JSON5 to catch syntax errors before using it.

Conclusion

JSON5, with its support for comments, significantly enhances the human-friendliness of JSON data. By allowing you to add explanations and notes directly within your files using single-line (`//`) and multi-line (`/* */`) comments, JSON5 makes configurations and complex data structures more understandable and maintainable.

If you frequently work with JSON files that are read or edited by humans, adopting JSON5 and a compatible formatter can streamline your workflow and reduce errors caused by misunderstandings. Just remember to use comments judiciously and ensure your tools support the JSON5 format.