JSON with Property Comments — A lightweight JSON variant that allows single-line comments // and trailing commas in JSON files.

Syntax

jsonpc follows these rules for comment:

1. Trailing commas in arrays and objects are allowed
2. Only single-line comments starting with // are supported
3. Comments must occupy an entire line
4. Multiple consecutive comment lines are allowed
5. Valid comment positions:
   1. Top of the file (before any JSON content)
   2. Bottom of the file (after all JSON content)
   3. Above property names

Other positions and block comments are not allowed.

Examples

// ✅ Valid: Top-level file comment
// ✅ Valid: Multiple consecutive comments allowed
{
  // ✅ Valid: Comment above property name
  "name": "Alice",

  // ✅ Valid: Comment above array element (primitive)
  "items": [
    // ❌ Invalid: Comment not above a property
    1,
    2,
  ],

  "users": [
    {
    // ✅ Valid: Comment above object property in array
    // ✅ Valid: 1 Multiple consecutive comments allowed
    // ✅ Valid: 2 Multiple consecutive comments allowed
      "name": "Bob"
    },
    // ❌ Invalid: Comment not above a property
    "sdaf"
  ],

  /* ❌ Invalid: Block comments not supported */
  "key": "value",
  // ❌ Invalid: Comment not above a property
}
// ✅ Valid: Bottom-level file comment

Usage

import { parse } from 'jsonpc-ts';

// Parse jsonpc text into an operatable instance
const jsonpc = parse(text);

// Get both value and comments for a property path
const entry = jsonpc.get('profile');
// → { value: { age: 25 }, comments: ['// Nested object comment'] }

// Get value only
const name = jsonpc.get('name')?.value;    // → "Alice"
const age = jsonpc.get('profile.age')?.value; // → 25
const age2 = jsonpc.get(['profile','age'])?.value; // → 25

// Get comments only
const comments = jsonpc.get('name')?.comments;
// → ['// This is a name comment']

// Handle non-existent paths
const entry = jsonpc.get('nonexistent');
// → undefined

jsonpc.set('profile', {
  value: { age: 26 },
  comments: ['Updated profile comment']
});
// Sets 'profile' to be an object with age 26 and updates its comments


// Set top-level comments
jsonpc.top = ['// New top comment'];

// Set bottom-level comments
jsonpc.bottom = ['// New bottom comment'];

Top and Bottom File Comments

import { parse } from 'jsonpc-ts';

const jsonpc = parse(text);

// Get top-level file comments
const topComments = jsonpc.top;
// → ['// This is a top comment', '// Another top comment']

// Get bottom-level file comments  
const bottomComments = jsonpc.bottom;
// → ['// This is a bottom comment']

// Get/Set top-level comments
jsonpc.top = ['New top comment'];

// Get/Set bottom-level comments
jsonpc.bottom = ['New bottom comment'];

// Release internal references and clear internal containers
jsonpc.destroy();

Serialization

// Serialize back to JSON text with comments
const output = jsonpc.stringify();

// Custom indentation and replacer
const custom = jsonpc.stringify(null, 4);

// Get clean JSON object without comments
const clean = jsonpc.toObject();
// → { name: "Alice", profile: { age: 25 }, items: [1, 2] }

Comparison with Alternatives

Solution	Custom Parser	Arbitrary Position Comments	Trailing Commas	Size
jsonpc	❌	❌	✅	Small
json5	✅	✅	✅	Large
JSONC	✅	✅	❌	Medium

jsonpc trades some flexibility for simplicity and performance by:

• Only allowing comments at specific, predictable positions (above properties)
• Using standard JSON parsing with comment pre-processing
• Maintaining a lightweight codebase

License

MIT

Contributing

Issues and Pull Requests are welcome!

Related Links

• GitHub Repository
• npm Package