Generate Documentation from Code

Category: Documentation October 1, 2025

Automatically generate comprehensive documentation from existing code including API docs, inline comments, and usage examples.

DocumentationCode GenerationAPI DocsAuto-documentation

# Generate Documentation from Code

Automatically generate comprehensive, well-structured documentation from existing source code, including function documentation, class documentation, and usage examples.

## Documentation Generation Scope

### 1. Module/File Documentation

**File Header**

/**

@module ModuleName
@description Brief description of what this module does
@author [Team/Author Name]
@since [Version] */


**Module Overview**
- Purpose and responsibilities
- Main exports and public API
- Dependencies and requirements
- Usage examples
- Related modules

### 2. Class Documentation

**Class Header Template**

/**

@class ClassName
@description Detailed description of the class purpose and behavior
@example
const instance = new ClassName(config);
instance.method();


**Class Components**
- Purpose and responsibility
- Constructor parameters
- Public methods and properties
- Private/protected members (internal docs)
- Inheritance and interfaces
- Usage patterns and examples
- Common pitfalls or important notes

### 3. Function/Method Documentation

**JSDoc/TSDoc Format**
```typescript
/**
 * Calculates the sum of two numbers and returns the result.
 * 
 * @param {number} a - The first number to add
 * @param {number} b - The second number to add
 * @param {Object} [options] - Optional configuration
 * @param {boolean} [options.round=false] - Whether to round the result
 * @returns {number} The sum of a and b
 * @throws {TypeError} If either parameter is not a number
 * 
 * @example
 * ```typescript
 * const result = sum(5, 3);
 * console.log(result); // 8
 * 
 * const rounded = sum(5.7, 3.2, { round: true });
 * console.log(rounded); // 9
 * ```
 * 
 * @since 1.0.0
 * @see {@link multiply} for multiplication operations
 */
function sum(a: number, b: number, options?: { round?: boolean }): number {
  const result = a + b;
  return options?.round ? Math.round(result) : result;
}

Function Documentation Elements

Brief description (first line)
Detailed description (if needed)
Parameters with types and descriptions
Return value with type
Exceptions/errors thrown
Usage examples (at least one)
Related functions/methods
Version introduced
Deprecation notices (if applicable)

4. Property/Variable Documentation

Property Documentation

/**
 * The maximum number of retry attempts for failed operations.
 * 
 * @type {number}
 * @default 3
 * @readonly
 */
const MAX_RETRIES = 3;

/**
 * Configuration options for the service.
 * 
 * @typedef {Object} ServiceConfig
 * @property {string} apiKey - API authentication key
 * @property {number} [timeout=5000] - Request timeout in milliseconds
 * @property {boolean} [debug=false] - Enable debug logging
 */

5. Type Definitions

TypeScript Types/Interfaces

/**
 * Represents a user in the system.
 * 
 * @interface User
 * @property {string} id - Unique identifier
 * @property {string} email - User's email address
 * @property {string} name - User's full name
 * @property {UserRole} role - User's role in the system
 * @property {Date} createdAt - Account creation timestamp
 */
interface User {
  id: string;
  email: string;
  name: string;
  role: UserRole;
  createdAt: Date;
}

/**
 * Available user roles.
 * 
 * @enum {string}
 */
enum UserRole {
  /** Standard user with basic permissions */
  USER = 'user',
  /** Administrator with full permissions */
  ADMIN = 'admin',
  /** Moderator with elevated permissions */
  MODERATOR = 'moderator'
}

6. API Documentation

REST API Endpoint Documentation

/**
 * @api {post} /api/users Create User
 * @apiName CreateUser
 * @apiGroup Users
 * @apiVersion 1.0.0
 * 
 * @apiDescription Creates a new user account with the provided information.
 * 
 * @apiHeader {String} Authorization Bearer token for authentication
 * @apiHeader {String} Content-Type application/json
 * 
 * @apiParam {String} email User's email address (must be unique)
 * @apiParam {String} name User's full name
 * @apiParam {String="user","admin"} [role="user"] User's role
 * 
 * @apiSuccess (201) {String} id Unique user identifier
 * @apiSuccess (201) {String} email User's email
 * @apiSuccess (201) {String} name User's name
 * @apiSuccess (201) {String} role User's role
 * @apiSuccess (201) {Date} createdAt Creation timestamp
 * 
 * @apiError (400) BadRequest Invalid request parameters
 * @apiError (401) Unauthorized Missing or invalid authentication
 * @apiError (409) Conflict Email already exists
 * 
 * @apiExample {curl} Example usage:
 *   curl -X POST https://api.example.com/api/users \
 *     -H "Authorization: Bearer YOUR_TOKEN" \
 *     -H "Content-Type: application/json" \
 *     -d '{"email":"user@example.com","name":"John Doe"}'
 * 
 * @apiSuccessExample {json} Success Response:
 *   HTTP/1.1 201 Created
 *   {
 *     "id": "user-123",
 *     "email": "user@example.com",
 *     "name": "John Doe",
 *     "role": "user",
 *     "createdAt": "2025-10-01T12:00:00Z"
 *   }
 * 
 * @apiErrorExample {json} Error Response:
 *   HTTP/1.1 400 Bad Request
 *   {
 *     "error": "VALIDATION_ERROR",
 *     "message": "Invalid email format"
 *   }
 */

7. Usage Examples

Comprehensive Examples

/**
 * @example Basic Usage
 * ```typescript
 * import { UserService } from './services/user.service';
 * 
 * const service = new UserService({
 *   apiKey: process.env.API_KEY
 * });
 * 
 * // Create a user
 * const user = await service.createUser({
 *   email: 'user@example.com',
 *   name: 'John Doe'
 * });
 * 
 * console.log(user.id); // 'user-123'
 * ```
 * 
 * @example Advanced Usage with Error Handling
 * ```typescript
 * try {
 *   const user = await service.createUser({
 *     email: 'user@example.com',
 *     name: 'John Doe',
 *     role: 'admin'
 *   });
 *   console.log('User created:', user);
 * } catch (error) {
 *   if (error.code === 'USER_EXISTS') {
 *     console.error('User already exists');
 *   } else {
 *     console.error('Failed to create user:', error);
 *   }
 * }
 * ```
 */

Documentation Best Practices

Writing Style

Use clear, concise language
Write in present tense
Use active voice
Start with a verb for functions (“Calculates…”, “Returns…”, “Validates…”)
Be specific and avoid vague terms

Content Guidelines

Document the “why” not just the “what”
Include edge cases and limitations
Document side effects
Explain complex algorithms
Provide context when needed
Link to related documentation

Code Examples

Include at least one example for public APIs
Show realistic use cases
Include error handling in examples
Test examples to ensure they work
Use proper formatting and indentation

Maintenance

Keep documentation synchronized with code
Update docs when changing signatures
Mark deprecated features clearly
Version documentation appropriately
Remove documentation for deleted code

Output Formats

Inline Documentation

JSDoc/TSDoc comments in source files
README files for modules/packages
Changelog files for version history

Generated Documentation

HTML documentation (JSDoc, TypeDoc)
Markdown files for docs sites
API specification (OpenAPI/Swagger)
Interactive API explorers

Documentation Tools

JavaScript/TypeScript: JSDoc, TypeDoc, Documentation.js
Python: Sphinx, pdoc, pydoc
Java: Javadoc
C#: XML documentation comments, DocFX
Go: godoc
Rust: rustdoc