The working developer's field notes

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A focused library of JavaScript and TypeScript patterns for the details you solve repeatedly—arrays, browser APIs, async flows, validation, and performance.

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FIELD NOTE · 010•••

function debounce(fn, delay) {

let timer;

return (...args) => {

clearTimeout(timer);

timer = setTimeout(

() => fn(...args), delay

);

};

}

Why it matters

Wait until a burst of input settles before running expensive work.

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30documented patterns

4practical categories

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Patterns worth keeping close

Selected for broad usefulness, readable implementations, and the kinds of edge cases that show up in production.

10TypeScript

Debounce Function

Delays function execution until after specified idle time, ideal for search input, autocomplete, and form validation

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11TypeScript

Async/Await Error Handler

Simplifies async/await error handling without try/catch blocks, returns [error, result] tuple

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30TypeScript

Generic Memoization Function

Caches function results based on arguments to avoid redundant computations

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Reference library

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30 results

TypeScriptType Checking

Precise Data Type Detection

Replaces typeof to solve inaccurate type checking issues (e.g., typeof null === 'object'), returns lowercase precise type string

Type CheckingUtility FunctionBasic

/**
 * Precise data type detection
 * @param value Value to be detected
 * @returns Type string (string/number/array/object/null/date etc.)

TypeScriptObject Manipulation

Deep Clone (Object/Array/Date/RegExp Support)

Solves reference type shallow copy issues, supports deep cloning of primitive types, objects, arrays, dates, and regular expressions to avoid affecting original data when modifying copies

Object ManipulationDeep CloneReference Type

/**
 * Deep clone function
 * @param target Value to be cloned
 * @returns New cloned value

TypeScriptArray Manipulation

Array Deduplication (Object/Array Support)

Supports deduplication of not only primitive types but also complex types like objects and arrays, using JSON.stringify to generate unique identifiers

Array ManipulationDeduplicationComplex Types

/**
 * Array deduplication (supports primitive + reference types)
 * @param arr Array to be deduplicated
 * @returns New deduplicated array

TypeScriptArray Manipulation

Array Grouping (Type-Safe Version)

Lightweight and type-safe alternative to lodash.groupBy, groups array elements by specified rules and returns structured grouping object

Array ManipulationGroupingType Safety

/**
 * Array grouping function
 * @param arr Array to be grouped
 * @param keyFn Function to generate grouping key

TypeScriptArray Manipulation

Safe Array Item Access

Prevents index out-of-bounds errors when accessing array elements, returns default value for invalid indices

Array ManipulationError PreventionSafe Access

/**
 * Safe array item access (prevents out-of-bounds errors)
 * @param arr Target array
 * @param index Target index

TypeScriptArray Manipulation

Array Flattening (Specified Depth)

Flattens nested arrays with configurable depth, perfect for processing multi-level nested data structures

Array ManipulationFlatteningNested Arrays

/**
 * Array flattening with configurable depth
 * @param arr Array to be flattened
 * @param depth Flattening depth (Infinity by default)

TypeScriptObject Manipulation

Object Property Filtering (Pick)

Creates a new object with only specified properties, ideal for removing unnecessary fields from API requests

Object ManipulationProperty FilteringData Sanitization

/**
 * Pick specified properties from object
 * @param obj Target object
 * @param keys Array of properties to keep

TypeScriptObject Manipulation

Object Property Omission (Omit)

Creates a new object excluding specified properties, useful for removing sensitive or unnecessary fields

Object ManipulationProperty OmissionData Security

/**
 * Omit specified properties from object
 * @param obj Target object
 * @param keys Array of properties to remove

TypeScriptPerformance

Throttle Function

Limits function execution frequency to specified interval, perfect for scroll/resize events and button clicks

PerformanceEvent HandlingThrottle

/**
 * Throttle function implementation
 * @param fn Function to throttle
 * @param delay Throttle interval in milliseconds

TypeScriptPerformance

Debounce Function

Delays function execution until after specified idle time, ideal for search input, autocomplete, and form validation

PerformanceEvent HandlingDebounce

/**
 * Debounce function implementation
 * @param fn Function to debounce
 * @param delay Idle time in milliseconds

TypeScriptAsync/Await

Async/Await Error Handler

Simplifies async/await error handling without try/catch blocks, returns [error, result] tuple

Async/AwaitError HandlingPromise

/**
 * Async/await error handler
 * @param promise Promise to execute
 * @returns Tuple [error, result]

TypeScriptLocalStorage

Local Storage with Expiry

Enhanced localStorage with automatic expiry, supports TTL (Time-To-Live) for stored items

LocalStorageCacheExpiry

/**
 * LocalStorage with expiry support
 */
const ExpiryStorage = {

TypeScriptRandom

Generate Random Unique ID

Generates cryptographically secure random IDs with configurable length, ideal for unique identifiers

RandomID GenerationUnique ID

/**
 * Generate random unique ID
 * @param length ID length (default: 16)
 * @returns Random alphanumeric ID

TypeScriptDate Handling

Format Date to Readable String

Converts Date object to customizable string format without external libraries like moment.js

Date HandlingFormattingUtility Function

/**
 * Format date to readable string
 * @param date Date object or timestamp
 * @param format Format string (YYYY=year, MM=month, DD=day, HH=hour, mm=minute, ss=second)

TypeScriptValidation

Email Address Validation

Robust email validation using RFC 5322 compliant regular expression

ValidationRegexForm Validation

/**
 * Validate email address format
 * @param email Email address to validate
 * @returns True if valid email, false otherwise

TypeScriptValidation

URL Validation

Validates URL format including http/https protocols, domain, and path

ValidationURLRegex

/**
 * Validate URL format
 * @param url URL to validate
 * @returns True if valid URL, false otherwise

TypeScriptString Manipulation

Convert String to CamelCase

Converts kebab-case, snake_case, or space-separated strings to camelCase

String ManipulationFormattingCamelCase

/**
 * Convert string to camelCase
 * @param str String to convert
 * @returns camelCase string

TypeScriptString Manipulation

Convert String to KebabCase

Converts camelCase, snake_case, or space-separated strings to kebab-case

String ManipulationFormattingKebabCase

/**
 * Convert string to kebab-case
 * @param str String to convert
 * @returns kebab-case string

TypeScriptDate Calculation

Calculate Age from Birthdate

Calculates accurate age from birthdate considering month and day

Date CalculationAgeUtility Function

/**
 * Calculate age from birthdate
 * @param birthdate Birthdate (Date object or ISO string)
 * @returns Calculated age in years

TypeScriptDOM

Smooth Scroll to Element

Smoothly scrolls to a DOM element with configurable offset and behavior

DOMScrollAnimation

/**
 * Smooth scroll to DOM element
 * @param element Target element or selector
 * @param offset Scroll offset in pixels

TypeScriptDevice Detection

Mobile Device Detection

Detects mobile devices (phones/tablets) using user agent string

Device DetectionUser AgentResponsive

/**
 * Detect if user is on mobile device
 * @returns True if mobile device, false otherwise
 */

TypeScriptClipboard

Copy Text to Clipboard

Cross-browser implementation to copy text to clipboard with promise-based API

ClipboardDOMUtility Function

/**
 * Copy text to clipboard
 * @param text Text to copy
 * @returns Promise resolving to true if successful, false otherwise

TypeScriptArray Generation

Generate Range Array

Generates array of numbers in specified range (like Python's range function)

Array GenerationUtility FunctionRange

/**
 * Generate array of numbers in specified range
 * @param start Start number (default: 0)
 * @param end End number (exclusive)

TypeScriptDOM

Check if Element is in Viewport

Detects if a DOM element is visible in the viewport (fully or partially)

DOMViewportScroll Detection

/**
 * Check if element is in viewport
 * @param element Target element
 * @param fullyInView Check if element is fully visible (default: false)

TypeScriptArray Manipulation

Shuffle Array (Fisher-Yates Algorithm)

Fair and unbiased array shuffling using the Fisher-Yates (Knuth) shuffle algorithm

Array ManipulationRandomAlgorithm

/**
 * Shuffle array using Fisher-Yates (Knuth) algorithm
 * @param arr Array to shuffle
 * @returns New shuffled array (original remains unchanged)

JavaScriptPerformance

Optimized Scroll Event Handling

Combines debounce with requestAnimationFrame for high-performance scroll event handling

PerformanceScrollEvent Handling

/**
 * Optimized scroll event handler
 * @param callback Function to execute on scroll
 * @param delay Debounce delay in milliseconds

TypeScriptNumber Formatting

Format Number as Currency

Formats numbers as currency strings with locale support (no external libraries)

Number FormattingCurrencyInternationalization

/**
 * Format number as currency string
 * @param amount Numeric amount
 * @param currency Currency code (default: 'USD')

TypeScriptAPI

Throttle API Requests

Prevents excessive API calls by throttling requests to specified rate limit

APIThrottleRate Limiting

/**
 * Throttle API requests with rate limiting
 * @param fn Async function to throttle
 * @param limit Maximum requests per minute

TypeScriptTypeScript

Type Guard for Non-Null Values

TypeScript type guard to filter out null/undefined values from arrays

TypeScriptType GuardNull Safety

/**
 * Type guard to check if value is not null/undefined
 * @param value Value to check
 * @returns Type predicate confirming non-null/undefined

TypeScriptPerformance

Generic Memoization Function

Caches function results based on arguments to avoid redundant computations

PerformanceMemoizationCaching

/**
 * Generic memoization function
 * @param fn Function to memoize
 * @returns Memoized function

Useful code.Explained properly.

Patterns worth keeping close

Debounce Function

Async/Await Error Handler

Generic Memoization Function

Find the pattern you need

Useful code.
Explained properly.