Tags
#php
#kotlin
#bash
#go
#sql
#rust
#typescript
#html
#java
#python
#files
#utils
#strings
#http
#concurrency
#async
#json
#arrays
#security
#types
#crypto
#database
#dates
#format
HTML
Select with Optgroup
`<optgroup label="...">` visually groups options inside a `<select>`. Renders as a non-selectable header in every browser; screen readers announce the group as context.
@admin
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.
TypeScript
groupBy (with key callback)
Group a list into a record keyed by whatever the callback returns. Like Lodash _.groupBy or the new Object.groupBy in modern runtimes. Generic enough to handle string, number, or symbol keys.
Go
CSV Read/Write with encoding/csv
`encoding/csv` parses RFC 4180 CSVs. Read row-by-row with `Read()` or all at once with `ReadAll()`. Same for writing — flush with `Writer.Flush()` before closing.
PHP
Unique by Callback
Like array_unique, but the uniqueness test is a callback that returns the key to dedupe by. Useful for "unique by ID" or "unique by lowercased email" across arrays of objects/rows.
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.
Go
Pointers — When and Why
Use pointers when you want to mutate the callee's value, share a large struct without copying, or distinguish "no value" via nil. Go has no pointer arithmetic — much safer than C.
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.
Kotlin
fold and scan
`fold` accumulates from a seed across all items. `runningFold` / `scan` yields every intermediate accumulator value — running totals, cumulative metrics.
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.
Go
Table-Driven Tests with t.Run
A table of test cases looped through `t.Run` gives every case its own name in the output, makes adding new cases trivial, and lets you run individual cases with `-run TestX/case_name`.
Kotlin
map / filter / reduce
The three classic functional combinators. Each takes a lambda and returns a new collection (or a single value for reduce). Chain freely — intermediate allocations only matter at very large scale (use `Sequence` then).
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.
SQL
EXPLAIN / EXPLAIN ANALYZE
`EXPLAIN` shows the query plan; `EXPLAIN ANALYZE` actually runs it and shows real timings. The first tool when a query is slow — look for sequential scans on big tables.
SQL
DELETE with JOIN / USING
Delete rows from one table conditional on a related table. PostgreSQL uses `USING`; MySQL uses join syntax in the DELETE. Run as a SELECT first to verify what you're about to remove.
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.
PHP
CSRF Token Generate + Verify
Per-session CSRF token helpers using hash_equals for constant-time comparison. Token is regenerated on logout but persists across requests within a session.