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#php
#kotlin
#bash
#go
#sql
#rust
#typescript
#html
#java
#python
#files
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#strings
#http
#concurrency
#async
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#format
SQL
LAG / LEAD — Previous and Next Row
Access the row before (`LAG`) or after (`LEAD`) the current one, in the window's order. Perfect for "delta from previous reading", session boundaries, etc.
@admin
SQL
EXISTS vs IN — Subquery Filtering
Both check membership. `EXISTS` is usually faster for big subqueries (stops at first hit). `IN` is more readable for small fixed lists. `NOT IN` is dangerous with NULLs — prefer `NOT EXISTS`.
TypeScript
clamp / lerp / mapRange
Three numeric utilities you reach for constantly in animation, UI math, and audio code. Generic enough to use anywhere, no Math.* dance required.
PHP
Try / Retry With Logging
Run a callable up to N times; log each failed attempt and bubble the last exception. Compact, no dependencies, useful for transient failures (S3 puts, email sends, etc.).
Kotlin
Parameterized Tests with JUnit 5
JUnit 5 + Kotlin: `@ParameterizedTest` runs the same test body with multiple input rows. `@CsvSource` for inline data, `@MethodSource` for complex args.
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.
SQL
Full-Text Search (PostgreSQL tsvector)
`tsvector` + `tsquery` is built-in full-text search — stemming, ranking, multilingual. For most apps this beats reaching for Elasticsearch right away.
TypeScript
AbortController-Wrapped Fetch
Wire an AbortController so you can cancel in-flight fetches when the user navigates away or types another search query. The optional timeout helper rejects automatically.
PHP
Cron Singleton with flock
Make sure only one copy of a long-running cron job runs at a time. Uses a non-blocking advisory lock on a sentinel file — second invocation exits immediately if the lock is held.
TypeScript
zip — Pair Two Arrays
Pair items from two arrays positionally into tuples. The result's length is the shorter of the two inputs. Useful for parallel arrays (labels + values, headers + rows).
TypeScript
Template Literal Types
Build string types out of other string types. Lets you express patterns like "every CSS event handler starts with on" in the type system itself, with autocomplete to match.
Kotlin
init Block + Constructor Order
`init { }` blocks run during construction, in declaration order, interleaved with property initializers. Use to validate the primary constructor or set up derived state.
JavaScript
Scroll to Element Smoothly
Scrolls the page to a target element with an optional pixel offset (useful when a fixed header is present). Uses the native scrollIntoView with smooth behaviour when supported, and falls back to a manual scrollTo with a configurable offset. Pass a CSS selector string or an Element reference.
Go
Concurrency Limit via Buffered Channel (Semaphore)
A buffered channel of size N is the simplest semaphore in Go — acquire by sending, release by receiving. Zero dependencies, no sync.Semaphore needed.
Python
ProcessPoolExecutor for CPU-Bound Work
Use processes (not threads) for CPU-bound work to sidestep the GIL. Functions must be picklable — define them at module level, not as locals or lambdas.
Kotlin
Data Classes — Records Done Right
`data class` auto-generates `equals`, `hashCode`, `toString`, `copy`, and `componentN` (destructuring). Replaces boilerplate POJOs / Records / classes-with-lombok in one line.
Kotlin
Nullable Types — String? and the ? Operator
Kotlin distinguishes `String` (never null) from `String?` (may be null) in the type system. The compiler refuses to compile code that could deref a possibly-null value — the famous "no more NullPointerException" feature.