jsdoc

name	jsdoc
description	Commenting and documentation guidelines. Auto-activate when the user discusses comments, documentation, docstrings, code clarity, API docs, JSDoc, or asks about commenting strategies.

Auto-activate when: User discusses comments, documentation, docstrings, code clarity, code quality, API docs, JSDoc, Python docstrings, or asks about commenting strategies. Core Principle

Write code that speaks for itself. Comment only when necessary to explain WHY, not WHAT.

Most code does not need comments. Well-written code with clear naming and structure is self-documenting.

The best comment is the one you don't need to write because the code is already obvious. The Commenting Philosophy When to Comment

✅ DO comment when explaining:

WHY something is done (business logic, design decisions)
Complex algorithms and their reasoning
Non-obvious trade-offs or constraints
Workarounds for bugs or limitations
API contracts and public interfaces
Regex patterns and what they match
Performance considerations or optimizations
Constants and magic numbers
Gotchas or surprising behaviors

❌ DON'T comment when:

The code is obvious and self-explanatory
The comment repeats the code (redundant)
Better naming would eliminate the need
The comment would become outdated quickly
It's decorative or organizational noise
It states what a standard language construct does

Comment Anti-Patterns ❌ 1. Obvious Comments

BAD:

counter = 0 # Initialize counter to zero counter += 1 # Increment counter by one user_name = input("Enter name: ") # Get user name from input

Better: No comment needed - the code is self-explanatory. ❌ 2. Redundant Comments

BAD:

def get_user_name(user): return user.name # Return the user's name

def calculate_total(items): # Loop through items and sum the prices total = 0 for item in items: total += item.price return total

Better:

def get_user_name(user): return user.name

def calculate_total(items): return sum(item.price for item in items)

❌ 3. Outdated Comments

BAD:

Calculate tax at 5% rate

tax = price * 0.08 # Actually 8%, comment is wrong

DEPRECATED: Use new_api_function() instead

def old_function(): # Still being used, comment is misleading pass

Better: Keep comments in sync with code, or remove them entirely. ❌ 4. Noise Comments

BAD:

Start of function

def calculate(): # Declare variable result = 0 # Return result return result

End of function

Better: Remove all of these comments. ❌ 5. Dead Code & Changelog Comments

BAD:

Don't comment out code - use version control

def old_function():

return "deprecated"

Don't maintain history in comments

Modified by John on 2023-01-15

Fixed bug reported by Sarah on 2023-02-03

Better: Delete the code. Git has the history. Good Comment Examples ✅ Complex Business Logic

Apply progressive tax brackets: 10% up to $10k, 20% above

This matches IRS publication 501 for 2024

def calculate_progressive_tax(income): if income <= 10000: return income * 0.10 else: return 1000 + (income - 10000) * 0.20

✅ Non-obvious Algorithms

Using Floyd-Warshall for all-pairs shortest paths

because we need distances between all nodes.

Time: O(n³), Space: O(n²)

for k in range(vertices): for i in range(vertices): for j in range(vertices): dist[i][j] = min(dist[i][j], dist[i][k] + dist[k][j])

✅ Regex Patterns

Match email format: [e-mail]

Allows letters, numbers, dots, hyphens in username

Requires valid domain and 2+ char extension

email_pattern = r'^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+.[a-zA-Z]{2,}$'

✅ API Constraints or Gotchas

GitHub API rate limit: 5000 requests/hour for authenticated users

We implement exponential backoff to handle rate limiting

await rate_limiter.wait() response = await fetch(github_api_url)

✅ Workarounds for Bugs

HACK: Workaround for bug in library v2.1.0

Remove after upgrading to v2.2.0

See: https://github.com/library/issues/123

if library_version == "2.1.0": apply_workaround()

Decision Framework

Before writing a comment, ask yourself: Step 1: Is the code self-explanatory?

If YES → No comment needed
If NO → Continue to step 2

Step 2: Would a better variable/function name eliminate the need?

If YES → Refactor the code instead
If NO → Continue to step 3

Step 3: Does this explain WHY, not WHAT?

If explaining WHAT → Refactor code to be clearer
If explaining WHY → Good comment candidate

Step 4: Will this help future maintainers?

If YES → Write the comment
If NO → Skip it

Special Cases for Comments Public APIs and Docstrings Python Docstrings

def calculate_compound_interest( principal: float, rate: float, time: int, compound_frequency: int = 1 ) -> float: """ Calculate compound interest using the standard formula.

Args:
    principal: Initial amount invested
    rate: Annual interest rate as decimal (e.g., 0.05 for 5%)
    time: Time period in years
    compound_frequency: Times per year interest compounds (default: 1)

Returns:
    Final amount after compound interest

Raises:
    ValueError: If any parameter is negative

Example:
    >>> calculate_compound_interest(1000, 0.05, 10)
    1628.89
"""
if principal < 0 or rate < 0 or time < 0:
    raise ValueError("Parameters must be non-negative")

# Compound interest formula: A = P(1 + r/n)^(nt)
return principal * (1 + rate / compound_frequency) ** (compound_frequency * time)

JavaScript/TypeScript JSDoc

/**

• Fetch user data from the API.
• @param {string} userId - The unique user identifier
• @param {Object} options - Configuration options
• @param {boolean} options.includeProfile - Include profile data (default: true)
• @param {number} options.timeout - Request timeout in ms (default: 5000)
• @returns {Promise} User object with requested fields
• @throws {Error} If userId is invalid or request fails
• @example
• const user = await fetchUser('123', { includeProfile: true }); */ async function fetchUser(userId, options = {}) { // Implementation }

Constants and Configuration

Based on network reliability studies (95th percentile)

MAX_RETRIES = 3

AWS Lambda timeout is 15s, leaving 5s buffer for cleanup

API_TIMEOUT = 10000 # milliseconds

Cache duration optimized for balance between freshness and load

See: docs/performance-tuning.md

CACHE_TTL = 300 # 5 minutes

Annotations for TODOs and Warnings

TODO: Replace with proper authentication after security review

Issue: #456

def temporary_auth(user): return True

WARNING: This function modifies the original array instead of creating a copy

def sort_in_place(arr): arr.sort() return arr

FIXME: Memory leak in production - investigate connection pooling

Ticket: JIRA-789

def get_connection(): return create_connection()

PERF: Consider caching this result if called frequently in hot path

def expensive_calculation(data): return complex_algorithm(data)

SECURITY: Validate input to prevent SQL injection before using in query

def build_query(user_input): sanitized = escape_sql(user_input) return f"SELECT * FROM users WHERE name = '{sanitized}'"

Common Annotation Keywords

TODO: - Work that needs to be done
FIXME: - Known bugs that need fixing
HACK: - Temporary workarounds
NOTE: - Important information or context
WARNING: - Critical information about usage
PERF: - Performance considerations
SECURITY: - Security-related notes
BUG: - Known bug documentation
REFACTOR: - Code that needs refactoring
DEPRECATED: - Soon-to-be-removed code

Refactoring Over Commenting Instead of Commenting Complex Code...

BAD: Complex code with comment

Check if user is admin or has special permissions

if user.role == "admin" or (user.permissions and "special" in user.permissions): grant_access()

...Extract to Named Function

GOOD: Self-explanatory through naming

def user_has_admin_access(user): return user.role == "admin" or has_special_permission(user)

def has_special_permission(user): return user.permissions and "special" in user.permissions

if user_has_admin_access(user): grant_access()

Language-Specific Examples JavaScript

// Good: Explains WHY we debounce // Debounce search to reduce API calls (500ms wait after last keystroke) const debouncedSearch = debounce(searchAPI, 500);

// Bad: Obvious let count = 0; // Initialize count to zero count++; // Increment count

// Good: Explains algorithm choice // Using Set for O(1) lookup instead of Array.includes() which is O(n) const seen = new Set(ids);

Python

Good: Explains the algorithm choice

Using binary search because data is sorted and we need O(log n) performance

index = bisect.bisect_left(sorted_list, target)

Bad: Redundant

def get_total(items): return sum(items) # Return the sum of items

Good: Explains why we're doing this

Extract to separate function for type checking in mypy

def validate_user(user): if not user or not user.id: raise ValueError("Invalid user") return user

TypeScript

// Good: Explains the type assertion // TypeScript can't infer this is never null after the check const element = document.getElementById('app') as HTMLElement;

// Bad: Obvious const sum = a + b; // Add a and b

// Good: Explains non-obvious behavior // spread operator creates shallow copy; use JSON for deep copy const newConfig = { ...config };

Comment Quality Checklist

Before committing, ensure your comments:

Explain WHY, not WHAT
Are grammatically correct and clear
Will remain accurate as code evolves
Add genuine value to code understanding
Are placed appropriately (above the code they describe)
Use proper spelling and professional language
Follow team conventions for annotation keywords
Could not be replaced by better naming or structure
Are not obvious statements about language features
Reference tickets/issues when applicable

Summary

Priority order:

Clear code - Self-explanatory through naming and structure
Good comments - Explain WHY when necessary
Documentation - API docs, docstrings for public interfaces
No comments - Better than bad comments that lie or clutter

Remember: Comments are a failure to make the code self-explanatory. Use them sparingly and wisely. Key Takeaways Goal Approach Reduce comments Improve naming, extract functions, simplify logic Improve clarity Use self-explanatory code structure, clear variable names Document APIs Use docstrings/JSDoc for public interfaces Explain WHY Comment only business logic, algorithms, workarounds Maintain accuracy Update comments when code changes, or remove them