customcommander

Observing state transitions with XState & RxJS

Objective

Create an observable that emits each time a specific transition is taken.

Problem

This "flip" machine keeps tossing the coin each time it lands on head. The machine reaches its final state when the side is tail:

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Testdouble.js Cheatsheet & Cookbook

Why use testdouble.js?

Suppose we need to test that a function calls another function:

function call(fn) {
  fn();
}

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RIS Specification

This is to the best of my knowledge the RIS specification as it was defined in 2011 by the original author. See https://en.wikipedia.org/wiki/RIS_(file_format)#cite_note-:1-5.

(Re)producing the dataset

Requirements

In order to run the scripts used to produce the dataset the following programs must be available on your system path:

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Canonical post for my Stack Overflow Q&A

How to use the Google Closure Compiler to browserify your Node.js library

I have this simple Node.js library:

mylib/
|- inc.js
|- index.js

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JSDoc Cheat Sheet

Things I found myself researching over and over without taking the time to write them down. Until now.

Table of Contents

1. Should I use {String} vs {string} or {Number} vs {number} ...?
2. Type Expression: Optional vs Nullable vs Non-nullable
3. When do I need to use the @function tag?

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Git Mining

Some scripts I use to mine data out of my Git repositories. Sharing in case it is useful to others.

Last commit for each year/month

git log --format="%cd %h" --date=short | sort -t- -k1,1n -k2,2n -u

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Spread vs assign

Abstract

In this article I compare the performance of the spread operator ... and the performance of the assignement operator = in the context of data transformation.

I show that using the spread operator isn't a trivial choice to make and I suggest that immutability and mutation don't have to be mutually exclusive. I also show how one-liner functions can be enriched with the comma operator ,.

What are we measuring?

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require('chromedriver');

const path = require('path');
const wd = require('selenium-webdriver');
const chrome = require('selenium-webdriver/chrome');

var builder = new wd.Builder();
var options = new chrome.Options();
var prefs = new wd.logging.Preferences();
var driver;

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/**
 * Return all permutations of given string.
 *
 * @example
 *   permute('abc');
 *   //=> ['abc', 'acb', 'bac', 'bca', 'cab', 'cba']
 * @param str {String}
 * @return {Array}
 */
function permute(str) {