Eugene Lazutkin uhop

Copying within an array: hand-written loops vs `Array#copyWithin`

Benchmark from lazutkin.com, the companion to Duff's device, part 2: copying within an array, which follows Duff's device in JavaScript.

The first post copied one array into another; its benchmark is in a separate gist. This one copies a range within one array, which is Array#copyWithin's domain, so the built-in and the hand-written loops race on equal terms.

Copying one array into another: hand-written loops and Duff's device

Benchmark from lazutkin.com, the companion to Duff's device in JavaScript.

The follow-up, Duff's device, part 2: copying within an array, asks the same question of a range copied inside one array, where Array#copyWithin competes; its benchmark is in a separate gist.

name: tufte-viz description: | Ideate and critique data visualizations using Edward Tufte's principles from "The Visual Display of Quantitative Information." Use this skill when: (1) Designing new data visualizations or charts (2) Critiquing or improving existing visualizations (3) Reviewing dashboards or reports for graphical integrity (4) Deciding between visualization approaches (5) Reducing chartjunk or improving data-ink ratio (6) Planning small multiples or high-density displays

GPG - SSH setup

Generating the master key

Here we create the master key. We want only Certify capability: we use the master key only to create the subkeys, Sign - Encrypt - Authenticate capabilities will be assigned to the subkeys.

Run the following command to start the master key generation process. Select the set your own capabilities creation process (type 8)

  ▶ gpg --full-generate-key --expert

Shell scripting with Markdown documents

alias ~~~=":<<'~~~sh'";:<<'~~~sh'

	// Benchmarks for "Exotic `goto`: generators and exceptions"
	// https://www.lazutkin.com/blog/2026-08-18-exotic-goto
	//
	// npm install
	// npm run bench # everything below, in order
	// npm run bench:escape:early # match at leaf 5, escape dominates
	// npm run bench:escape:late # match at leaf 950, traversal dominates
	//
	// Escaping a nested traversal: labeled break vs a relayed return vs throw.
	// gadgets -> gizmos -> doodads, 10 x 10 x 10 = 1000 leaves.

	## Workflow Orchestration

	### 1. Plan Node Default
	- Enter plan mode for ANY non-trivial task (3+ steps or architectural decisions)
	- If something goes sideways, STOP and re-plan immediately
	- don't keep pushing
	- Use plan mode for verification steps, not just building
	- Write detailed specs upfront to reduce ambiguity

	### 2. Subagent Strategy

	const fastPow = (x, n) => {
	if (x <= 0) return 0;
	if (n === 0) return 1;
	if (n === 1) return x;

	const result = fastPow(x, n >> 1);

	return (n & 1) ? result * x : result;
	};

	// doubly linked list

	const removeNode = node => {
	node.prev.next = node.next;
	node.next.prev = node.prev;
	node.prev = node.next = node;
	return node;
	};

	class DLL {

	import {up, down} from './min-heap.js';

	// more efficient operations based on up() and down()
	// WARNING: untested (if I wrote comprehensive tests it wouldn't be a gist, would it?)

	const replaceTop = (heapArray, value, less) => {
	const top = heapArray[0];
	heapArray[0] = value;
	down(heapArray, 0, less);
	return top;