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#php
#kotlin
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#typescript
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#java
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#format
JavaScript
Queue (Async Task Queue)
A serialised async task queue that executes queued async functions one at a time, in order. Useful for sequencing operations that must not run concurrently (file writes, ordered API mutations, step-by-step wizards). add() returns a Promise that resolves/rejects when that specific task completes.
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SQL
INNER JOIN — Match Rows in Both Tables
Returns rows where the join condition matches in BOTH tables. The default JOIN. Use table aliases (`u`, `o`) for readability when joining 3+ tables.
SQL
Cohort Retention Analysis
Group users by their signup week, then count how many were still active in each subsequent week. The classic SaaS retention table — entirely in SQL.
JavaScript
Range Generator
Generates an array of numbers from start to end (inclusive) with an optional step. Supports negative steps for counting down. Covers the most common use case of Array.from({ length: n }, (_, i) => i) with a much cleaner API, and handles arbitrary start/end/step combinations.
JavaScript
Format Currency
Formats a number as a locale-aware currency string using the built-in Intl.NumberFormat API. Supports any ISO 4217 currency code and any BCP 47 locale tag. No external library required — handles symbol placement, thousands separators, and decimal places automatically per locale rules.
JavaScript
Curry Function
Transforms a multi-argument function into a chain of single-argument functions. Each call returns a new function until all arguments are supplied, then the original function executes. Enables partial application and cleaner function composition pipelines.
JavaScript
Validate Email Address
Validates an email address using a battle-tested regex that covers the vast majority of real-world addresses without being overly strict. For server-side code, pair this with a confirmation email step — client-side regex alone is not a security measure. Returns a boolean for easy conditional use.
JavaScript
Pipe & Compose
pipe applies a list of functions left-to-right (first function runs first), while compose applies them right-to-left. Both pass the result of each step as input to the next. Fundamental building blocks for functional programming in JavaScript — build data transformation pipelines without intermediate variables.
JavaScript
Group Array by Key
Groups an array of objects into a map keyed by the result of a callback or property name. Uses Object.groupBy when available (ES2024) and falls back to a reduce implementation. Returns an object whose keys are the group names and values are arrays of matching items.
JavaScript
Capitalize Words (Title Case)
Converts a string to title case by capitalising the first letter of each word. Handles multiple spaces and mixed-case input. Optionally skips common English stopwords (a, an, the, of, in, …) so article/preposition words are not capitalised in the middle of a title — matching standard editorial style guides.
JavaScript
Generate Initials Avatar (Canvas)
Draws a coloured circular avatar with up to two initials on an HTML5 Canvas and returns it as a data URL. Generates a consistent background colour from the name string so the same user always gets the same colour. Useful as a fallback when a user has no profile photo.
JavaScript
Deep Equal Comparison
Performs a recursive structural equality check between two values. Handles primitives, arrays, objects, Dates, Maps, Sets, null, and undefined. Faster than JSON.stringify comparison (which ignores undefined and Map/Set), and avoids the false-positive trap of == or Object.is for nested structures.
JavaScript
Parse URL Query String
Parses a URL query string into a plain key-value object. Uses the built-in URLSearchParams API — no regex required. Handles duplicate keys (returns the first value), percent-encoded characters, and works with both full URLs and raw query strings. Pairs nicely with buildQueryString.
JavaScript
Base64 Encode & Decode (Unicode-safe)
Encodes and decodes strings to/from Base64. The native btoa/atob only handles Latin-1 characters, so these wrappers use TextEncoder/Uint8Array to handle the full Unicode range including emoji and CJK characters. Useful for encoding binary data, tokens, and payloads for URLs or localStorage.
JavaScript
Deep Clone Object
Creates a true deep copy of any serialisable object or array — nested objects, arrays, dates (as ISO strings). Uses structuredClone when available (modern browsers/Node 17+) and falls back to JSON round-trip for older environments. Does not handle functions, undefined, or circular references.
JavaScript
Truncate String
Truncates a string to a maximum character length and appends an ellipsis (or custom suffix). The smart version breaks at the last word boundary to avoid cutting in the middle of a word, making truncated text look natural in card previews, notifications, and list views.
JavaScript
Hex ↔ RGB Conversion
Converts between hex colour strings (#rrggbb / #rgb) and RGB component objects. hexToRgb parses both shorthand and full hex formats. rgbToHex converts R, G, B integers (0–255) back to a hex string. Handy for colour manipulation, generating CSS variables, and passing colour data between libraries.