HTML

Form Validation Attributes

Built-in client-side validation: `required`, `pattern`, `minlength`/`maxlength`, `min`/`max`. The browser blocks submission and shows a native error if anything fails. Always validate on the server too.

5h ago 0

Bash

Array Basics (index + iterate)

Bash 4+ arrays — declare, access by index, get all elements with [@], length with #. The quoting matters: "${arr[@]}" preserves each element; ${arr[@]} word-splits.

5h ago 0

Bash

Recursive Directory Walker with Predicate

Use `find -print0` + `read -d ""` to safely iterate filenames that may contain spaces, newlines, or quotes. Standard bash for-loop over `find` output breaks on these.

5h ago 0

HTML

Search Form with Accessible Label

A search input usually has a visible-only icon — but screen readers need a real label. Pair a visually-hidden `<label>` with the icon, OR use `aria-label` on the input.

5h ago 0

Kotlin

withContext — Switching Dispatchers

`withContext(dispatcher)` suspends the calling coroutine, runs the block on the given dispatcher, returns the result. Use `Dispatchers.IO` for blocking I/O, `Default` for CPU work, `Main` for UI updates.

5h ago 0

PHP

cURL Multipart File Upload

Upload one or more files via multipart/form-data using cURL's CURLFile abstraction. No manual boundary or body construction needed.

5h ago 0

Rust

Builder Pattern with Method Chaining

Construct complex objects step-by-step with `self`-returning methods. Type-state can enforce required vs. optional fields at compile time — but the simple version is plenty for most cases.

5h ago 0

SQL

CASE WHEN — Conditional Values

Inline if/else inside a SELECT, ORDER BY, or aggregation. The Swiss-army knife for converting raw column values into labels or buckets.

5h ago 0

SQL

Soft Delete with Partial Index

Set a `deleted_at` timestamp instead of physically removing rows — preserves history and lets you "undelete". Pair with a partial index for fast queries that skip the soft-deleted rows.

5h ago 0

PHP

Number to Ordinal (1st, 2nd, 3rd)

Convert an integer to its English ordinal form ("1st", "2nd", "3rd", "11th", "22nd", "103rd"). Pure rule-based; no library needed.

5h ago 0

Go

Type Switches

When you have an `interface{}` (or any) and need to dispatch on its underlying type, use `switch v := x.(type)`. Cleaner than a chain of type-assertions.

5h ago 0

SQL

RETURNING — Get Back What You Wrote

PostgreSQL `RETURNING *` returns the rows affected by an INSERT/UPDATE/DELETE — no separate SELECT round-trip needed. SQL Server has `OUTPUT`; MySQL added `RETURNING` in MariaDB and 8.0.31+.

5h ago 0

PHP

Get Nested Value by Dot Path

Read deeply-nested array values like Lodash _.get(). Use a "a.b.c" string instead of nested isset checks; returns a default on any missing segment.

5h ago 0

Rust

Walk a Directory Tree

`walkdir` recursively iterates every entry under a path, skipping inaccessible directories cleanly. The standard-library alternative requires manual recursion.

5h ago 0

Kotlin

Sorting Collections

`sortedBy { ... }` returns a sorted copy. `sortedWith(compareBy { ... })` chains tie-breakers cleanly. Avoid `sortBy` (in-place) on read-only lists.

5h ago 0

SQL

Indexes — B-tree, Partial, Composite

Indexes are the difference between a 50ms query and a 50s one. Composite indexes match queries that filter / sort on the columns in order; partial indexes skip irrelevant rows for big space savings.

5h ago 0

Kotlin

Coroutine Timeout with withTimeout

`withTimeout(ms) { ... }` cancels the inner coroutine if it doesn't finish in time and throws `TimeoutCancellationException`. `withTimeoutOrNull` returns null instead.

5h ago 0

Go

sync.Once — Lazy One-Time Initialization

Run a function exactly once, even from many goroutines. Standard pattern for lazy singletons, expensive setup, and one-time configuration.

5h ago 0

SQL

Conditional Aggregation (FILTER / CASE)

Count or sum subsets of rows in a single GROUP BY pass. PostgreSQL has the cleaner `FILTER` clause; everyone else uses `SUM(CASE WHEN ...)`.

5h ago 0

Kotlin

minOf / maxOf / sumOf / averageOf

Numerical reducers with a selector lambda — much cleaner than `.map { ... }.max()` chains. `sumOf` is type-aware (returns Int, Long, Double, BigDecimal as appropriate).

5h ago 0

PHP

Constant-Time String Compare

Compare two strings in constant time to avoid timing-attack leaks when checking secrets like API keys, session tokens, or HMAC signatures. Always use hash_equals — never ===.

5h ago 0

Rust

Atomic Counter (lock-free)

For shared counters and flags, `AtomicU64` / `AtomicBool` etc. are much faster than `Mutex`. Operations like `fetch_add` are single CPU instructions on most architectures.

5h ago 0

Kotlin

Coroutines — suspend Function Basics

`suspend fun` can be paused and resumed without blocking a thread. Call only from another `suspend` function or a coroutine builder (`launch`, `runBlocking`, `async`).

5h ago 0

Kotlin

async / await for Parallel Results

`async` returns a `Deferred<T>` — like a Future. Use it when you need a RESULT back, in parallel. Call `.await()` to get the value (suspends until ready).

5h ago 0

Kotlin

coroutineScope and Structured Concurrency

`coroutineScope { }` waits for ALL its children before returning. If any child throws, the others are cancelled. The cornerstone of structured concurrency — no leaked coroutines.

5h ago 0

Kotlin

lazy — Lazily Computed val

`by lazy { ... }` runs the block on first access, caches the result. Default mode is thread-safe (synchronized). Perfect for expensive initialization where you might never need the value.

5h ago 0

PHP

Singleton Trait

A reusable trait that turns any class into a lazily-instantiated singleton with a single ::instance() accessor. Throws on clone/wakeup to prevent accidental duplication.

5h ago 0

Go

Minimal net/http Server

The standard library ships a production-quality HTTP server. `http.HandleFunc` registers a function; `http.ListenAndServe` blocks forever serving requests.

5h ago 0

Kotlin

windowed and chunked

`chunked(n)` splits a list into NON-overlapping pieces of size n. `windowed(n)` slides a fixed-size window across — overlapping. Useful for moving averages, n-grams, batch APIs.

5h ago 0

Go

Pipeline (channel chain)

A pipeline is a chain of stages connected by channels — each stage runs in its own goroutine. Classic Go pattern for streaming transformations with backpressure built in.

5h ago 0