Coding Standards & Best Practices
Universal coding standards applicable across all projects.
Code Quality Principles
1. Readability First
Code is read more than written
Clear variable and function names
Self-documenting code preferred over comments
Consistent formatting
2. KISS (Keep It Simple, Stupid)
Simplest solution that works
Avoid over-engineering
No premature optimization
Easy to understand > clever code
3. DRY (Don't Repeat Yourself)
Extract common logic into functions
Create reusable components
Share utilities across modules
Avoid copy-paste programming
4. YAGNI (You Aren't Gonna Need It)
Don't build features before they're needed
Avoid speculative generality
Add complexity only when required
Start simple, refactor when needed
TypeScript/JavaScript Standards
Variable Naming
// ✅ GOOD: Descriptive names
const
marketSearchQuery
=
'election'
const
isUserAuthenticated
=
true
const
totalRevenue
=
1000
// ❌ BAD: Unclear names
const
q
=
'election'
const
flag
=
true
const
x
=
1000
Function Naming
// ✅ GOOD: Verb-noun pattern
async
function
fetchMarketData
(
marketId
:
string
)
{
}
function
calculateSimilarity
(
a
:
number
[
]
,
b
:
number
[
]
)
{
}
function
isValidEmail
(
email
:
string
)
:
boolean
{
}
// ❌ BAD: Unclear or noun-only
async
function
market
(
id
:
string
)
{
}
function
similarity
(
a
,
b
)
{
}
function
email
(
e
)
{
}
Immutability Pattern (CRITICAL)
// ✅ ALWAYS use spread operator
const
updatedUser
=
{
...
user
,
name
:
'New Name'
}
const
updatedArray
=
[
...
items
,
newItem
]
// ❌ NEVER mutate directly
user
.
name
=
'New Name'
// BAD
items
.
push
(
newItem
)
// BAD
Error Handling
// ✅ GOOD: Comprehensive error handling
async
function
fetchData
(
url
:
string
)
{
try
{
const
response
=
await
fetch
(
url
)
if
(
!
response
.
ok
)
{
throw
new
Error
(
HTTP
${
response
.
status
}
:
${
response
.
statusText
}
)
}
return
await
response
.
json
(
)
}
catch
(
error
)
{
console
.
error
(
'Fetch failed:'
,
error
)
throw
new
Error
(
'Failed to fetch data'
)
}
}
// ❌ BAD: No error handling
async
function
fetchData
(
url
)
{
const
response
=
await
fetch
(
url
)
return
response
.
json
(
)
}
Async/Await Best Practices
// ✅ GOOD: Parallel execution when possible
const
[
users
,
markets
,
stats
]
=
await
Promise
.
all
(
[
fetchUsers
(
)
,
fetchMarkets
(
)
,
fetchStats
(
)
]
)
// ❌ BAD: Sequential when unnecessary
const
users
=
await
fetchUsers
(
)
const
markets
=
await
fetchMarkets
(
)
const
stats
=
await
fetchStats
(
)
Type Safety
// ✅ GOOD: Proper types
interface
Market
{
id
:
string
name
:
string
status
:
'active'
|
'resolved'
|
'closed'
created_at
:
Date
}
function
getMarket
(
id
:
string
)
:
Promise
<
Market
{ // Implementation } // ❌ BAD: Using 'any' function getMarket ( id : any ) : Promise < any
{ // Implementation } React Best Practices Component Structure // ✅ GOOD: Functional component with types interface ButtonProps { children : React . ReactNode onClick : ( ) => void disabled ? : boolean variant ? : 'primary' | 'secondary' } export function Button ( { children , onClick , disabled = false , variant = 'primary' } : ButtonProps ) { return ( < button onClick = { onClick } disabled = { disabled } className = {
btn btn- ${ variant }}{ children } < / button
) } // ❌ BAD: No types, unclear structure export function Button ( props ) { return < button onClick = { props . onClick }
{ props . children } < / button
} Custom Hooks // ✅ GOOD: Reusable custom hook export function useDebounce < T
( value : T , delay : number ) : T { const [ debouncedValue , setDebouncedValue ] = useState < T
( value ) useEffect ( ( ) => { const handler = setTimeout ( ( ) => { setDebouncedValue ( value ) } , delay ) return ( ) => clearTimeout ( handler ) } , [ value , delay ] ) return debouncedValue } // Usage const debouncedQuery = useDebounce ( searchQuery , 500 ) State Management // ✅ GOOD: Proper state updates const [ count , setCount ] = useState ( 0 ) // Functional update for state based on previous state setCount ( prev => prev + 1 ) // ❌ BAD: Direct state reference setCount ( count + 1 ) // Can be stale in async scenarios Conditional Rendering // ✅ GOOD: Clear conditional rendering { isLoading && < Spinner /
} { error && < ErrorMessage error = { error } /
} { data && < DataDisplay data = { data } /
} // ❌ BAD: Ternary hell { isLoading ? < Spinner /
: error ? < ErrorMessage error = { error } /
: data ? < DataDisplay data = { data } /
: null } API Design Standards REST API Conventions GET /api/markets # List all markets GET /api/markets/:id # Get specific market POST /api/markets # Create new market PUT /api/markets/:id # Update market (full) PATCH /api/markets/:id # Update market (partial) DELETE /api/markets/:id # Delete market
Query parameters for filtering
- GET /api/markets?status=active&limit=10&offset=0
- Response Format
- // ✅ GOOD: Consistent response structure
- interface
- ApiResponse
- <
- T
- >
- {
- success
- :
- boolean
- data
- ?
- :
- T
- error
- ?
- :
- string
- meta
- ?
- :
- {
- total
- :
- number
- page
- :
- number
- limit
- :
- number
- }
- }
- // Success response
- return
- NextResponse
- .
- json
- (
- {
- success
- :
- true
- ,
- data
- :
- markets
- ,
- meta
- :
- {
- total
- :
- 100
- ,
- page
- :
- 1
- ,
- limit
- :
- 10
- }
- }
- )
- // Error response
- return
- NextResponse
- .
- json
- (
- {
- success
- :
- false
- ,
- error
- :
- 'Invalid request'
- }
- ,
- {
- status
- :
- 400
- }
- )
- Input Validation
- import
- {
- z
- }
- from
- 'zod'
- // ✅ GOOD: Schema validation
- const
- CreateMarketSchema
- =
- z
- .
- object
- (
- {
- name
- :
- z
- .
- string
- (
- )
- .
- min
- (
- 1
- )
- .
- max
- (
- 200
- )
- ,
- description
- :
- z
- .
- string
- (
- )
- .
- min
- (
- 1
- )
- .
- max
- (
- 2000
- )
- ,
- endDate
- :
- z
- .
- string
- (
- )
- .
- datetime
- (
- )
- ,
- categories
- :
- z
- .
- array
- (
- z
- .
- string
- (
- )
- )
- .
- min
- (
- 1
- )
- }
- )
- export
- async
- function
- POST
- (
- request
- :
- Request
- )
- {
- const
- body
- =
- await
- request
- .
- json
- (
- )
- try
- {
- const
- validated
- =
- CreateMarketSchema
- .
- parse
- (
- body
- )
- // Proceed with validated data
- }
- catch
- (
- error
- )
- {
- if
- (
- error
- instanceof
- z
- .
- ZodError
- )
- {
- return
- NextResponse
- .
- json
- (
- {
- success
- :
- false
- ,
- error
- :
- 'Validation failed'
- ,
- details
- :
- error
- .
- errors
- }
- ,
- {
- status
- :
- 400
- }
- )
- }
- }
- }
- File Organization
- Project Structure
- src/
- ├── app/ # Next.js App Router
- │ ├── api/ # API routes
- │ ├── markets/ # Market pages
- │ └── (auth)/ # Auth pages (route groups)
- ├── components/ # React components
- │ ├── ui/ # Generic UI components
- │ ├── forms/ # Form components
- │ └── layouts/ # Layout components
- ├── hooks/ # Custom React hooks
- ├── lib/ # Utilities and configs
- │ ├── api/ # API clients
- │ ├── utils/ # Helper functions
- │ └── constants/ # Constants
- ├── types/ # TypeScript types
- └── styles/ # Global styles
- File Naming
- components/Button.tsx # PascalCase for components
- hooks/useAuth.ts # camelCase with 'use' prefix
- lib/formatDate.ts # camelCase for utilities
- types/market.types.ts # camelCase with .types suffix
- Comments & Documentation
- When to Comment
- // ✅ GOOD: Explain WHY, not WHAT
- // Use exponential backoff to avoid overwhelming the API during outages
- const
- delay
- =
- Math
- .
- min
- (
- 1000
- *
- Math
- .
- pow
- (
- 2
- ,
- retryCount
- )
- ,
- 30000
- )
- // Deliberately using mutation here for performance with large arrays
- items
- .
- push
- (
- newItem
- )
- // ❌ BAD: Stating the obvious
- // Increment counter by 1
- count
- ++
- // Set name to user's name
- name
- =
- user
- .
- name
- JSDoc for Public APIs
- /**
- * Searches markets using semantic similarity.
- *
- * @param query - Natural language search query
- * @param limit - Maximum number of results (default: 10)
- * @returns Array of markets sorted by similarity score
- * @throws {Error} If OpenAI API fails or Redis unavailable
- *
- * @example
- * ```typescript
- * const results = await searchMarkets('election', 5)
- * console.log(results[0].name) // "Trump vs Biden"
- * ```
- */
- export
- async
- function
- searchMarkets
- (
- query
- :
- string
- ,
- limit
- :
- number
- =
- 10
- )
- :
- Promise
- <
- Market
- [
- ]
- >
- {
- // Implementation
- }
- Performance Best Practices
- Memoization
- import
- {
- useMemo
- ,
- useCallback
- }
- from
- 'react'
- // ✅ GOOD: Memoize expensive computations
- const
- sortedMarkets
- =
- useMemo
- (
- (
- )
- =>
- {
- return
- markets
- .
- sort
- (
- (
- a
- ,
- b
- )
- =>
- b
- .
- volume
- -
- a
- .
- volume
- )
- }
- ,
- [
- markets
- ]
- )
- // ✅ GOOD: Memoize callbacks
- const
- handleSearch
- =
- useCallback
- (
- (
- query
- :
- string
- )
- =>
- {
- setSearchQuery
- (
- query
- )
- }
- ,
- [
- ]
- )
- Lazy Loading
- import
- {
- lazy
- ,
- Suspense
- }
- from
- 'react'
- // ✅ GOOD: Lazy load heavy components
- const
- HeavyChart
- =
- lazy
- (
- (
- )
- =>
- import
- (
- './HeavyChart'
- )
- )
- export
- function
- Dashboard
- (
- )
- {
- return
- (
- <
- Suspense fallback
- =
- {
- <
- Spinner
- /
- >
- }
- >
- <
- HeavyChart
- /
- >
- <
- /
- Suspense
- >
- )
- }
- Database Queries
- // ✅ GOOD: Select only needed columns
- const
- {
- data
- }
- =
- await
- supabase
- .
- from
- (
- 'markets'
- )
- .
- select
- (
- 'id, name, status'
- )
- .
- limit
- (
- 10
- )
- // ❌ BAD: Select everything
- const
- {
- data
- }
- =
- await
- supabase
- .
- from
- (
- 'markets'
- )
- .
- select
- (
- '*'
- )
- Testing Standards
- Test Structure (AAA Pattern)
- test
- (
- 'calculates similarity correctly'
- ,
- (
- )
- =>
- {
- // Arrange
- const
- vector1
- =
- [
- 1
- ,
- 0
- ,
- 0
- ]
- const
- vector2
- =
- [
- 0
- ,
- 1
- ,
- 0
- ]
- // Act
- const
- similarity
- =
- calculateCosineSimilarity
- (
- vector1
- ,
- vector2
- )
- // Assert
- expect
- (
- similarity
- )
- .
- toBe
- (
- 0
- )
- }
- )
- Test Naming
- // ✅ GOOD: Descriptive test names
- test
- (
- 'returns empty array when no markets match query'
- ,
- (
- )
- =>
- {
- }
- )
- test
- (
- 'throws error when OpenAI API key is missing'
- ,
- (
- )
- =>
- {
- }
- )
- test
- (
- 'falls back to substring search when Redis unavailable'
- ,
- (
- )
- =>
- {
- }
- )
- // ❌ BAD: Vague test names
- test
- (
- 'works'
- ,
- (
- )
- =>
- {
- }
- )
- test
- (
- 'test search'
- ,
- (
- )
- =>
- {
- }
- )
- Code Smell Detection
- Watch for these anti-patterns:
- 1. Long Functions
- // ❌ BAD: Function > 50 lines
- function
- processMarketData
- (
- )
- {
- // 100 lines of code
- }
- // ✅ GOOD: Split into smaller functions
- function
- processMarketData
- (
- )
- {
- const
- validated
- =
- validateData
- (
- )
- const
- transformed
- =
- transformData
- (
- validated
- )
- return
- saveData
- (
- transformed
- )
- }
- 2. Deep Nesting
- // ❌ BAD: 5+ levels of nesting
- if
- (
- user
- )
- {
- if
- (
- user
- .
- isAdmin
- )
- {
- if
- (
- market
- )
- {
- if
- (
- market
- .
- isActive
- )
- {
- if
- (
- hasPermission
- )
- {
- // Do something
- }
- }
- }
- }
- }
- // ✅ GOOD: Early returns
- if
- (
- !
- user
- )
- return
- if
- (
- !
- user
- .
- isAdmin
- )
- return
- if
- (
- !
- market
- )
- return
- if
- (
- !
- market
- .
- isActive
- )
- return
- if
- (
- !
- hasPermission
- )
- return
- // Do something
- 3. Magic Numbers
- // ❌ BAD: Unexplained numbers
- if
- (
- retryCount
- >
- 3
- )
- {
- }
- setTimeout
- (
- callback
- ,
- 500
- )
- // ✅ GOOD: Named constants
- const
- MAX_RETRIES
- =
- 3
- const
- DEBOUNCE_DELAY_MS
- =
- 500
- if
- (
- retryCount
- >
- MAX_RETRIES
- )
- {
- }
- setTimeout
- (
- callback
- ,
- DEBOUNCE_DELAY_MS
- )
- Remember
- Code quality is not negotiable. Clear, maintainable code enables rapid development and confident refactoring. When to Use This skill is applicable to execute the workflow or actions described in the overview.