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#php
#kotlin
#bash
#go
#sql
#rust
#typescript
#html
#java
#python
#files
#utils
#strings
#http
#concurrency
#async
#json
#arrays
#security
#types
#crypto
#database
#dates
#format
Kotlin
Compose Modifier Chain
`Modifier` is how you customize composables — padding, click handlers, background, size, alignment. Order matters: each modifier wraps the previous one.
@admin
Go
Sentinel Errors (var ErrFoo = errors.New)
Sentinel errors are package-level singletons you can compare against with `errors.Is`. Use sparingly — they're part of your package's API surface and changing them is a breaking change.
Go
Error Wrapping with %w
`fmt.Errorf` with `%w` wraps an inner error inside an outer one, preserving the chain. Callers can use `errors.Is` / `errors.As` to inspect any level of the chain.
Kotlin
Sorting Collections
`sortedBy { ... }` returns a sorted copy. `sortedWith(compareBy { ... })` chains tie-breakers cleanly. Avoid `sortBy` (in-place) on read-only lists.
Rust
impl Trait — Static Dispatch Returns
When you want to return a complex iterator chain or closure, you don't need to spell out the type. `impl Trait` lets the compiler infer the concrete type while exposing only the API contract.
JavaScript
Rate Limiter (Token Bucket)
Implements a token-bucket rate limiter that allows a burst of calls up to a maximum capacity, then replenishes tokens at a steady rate. Useful for throttling outbound API requests, user-facing actions, or any operation where you need to allow occasional bursts without exceeding a sustained rate.
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.
Java
JUnit 5 — Parameterized Tests
`@ParameterizedTest` runs the same test with multiple inputs. Use `@CsvSource`, `@MethodSource`, or `@EnumSource` for data. Eliminates copy-paste in test classes.
Bash
Generate a Random Password
Three approaches: pwgen (purpose-built), openssl (universally available), /dev/urandom + tr (zero deps). Pick by what's installed.
PHP
Stream Large CSV with Generator
Iterate over a CSV file row-by-row without ever loading the whole file into memory. Uses a generator so consumers can foreach naturally and PHP cleans up the file handle.
Java
BufferedReader / BufferedWriter
For large files or line-oriented protocols, wrap a Reader/Writer in `Buffered*`. Reduces per-call overhead from many small reads to fewer large ones. Always close with try-with-resources.
SQL
ROW_NUMBER OVER PARTITION
Number rows within a partition — the most common "give me the Nth thing per group" pattern. Pair with a WHERE rn = 1 in an outer query to keep just the top row per group.
Go
struct Tags for JSON Marshaling
Backtick string tags on struct fields control how `encoding/json` serializes them — rename to camelCase, omit zero values, skip entirely. The same tag system is used by many other libraries.
Bash
Read Single Keystroke Without Enter
For menus and confirm prompts where you want one-key response (no need to press Enter). -n 1 reads exactly one character, -s silences the echo.
HTML
JSON-LD Structured Data (Schema.org)
JSON-LD is Google's preferred way to mark up structured data for rich search results. Drop it in a <script type="application/ld+json"> tag in <head>. Validate with Google's Rich Results Test.
Go
Benchmarks with testing.B
`BenchmarkXxx(b *testing.B)` functions are run by `go test -bench`. `b.N` is the loop count the framework auto-tunes; report results in ns/op, allocs/op.
HTML
Video Element with Captions
`<video>` with multiple `<source>` formats (MP4 + WebM), `controls`, `poster`, and a captions track via `<track kind="captions">`. All shipped with the browser — no JS player needed.