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Eirik L. Vullum eiriklv

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joshdover /
Last active July 18, 2023 22:43
Idiomatic React Testing Patterns

Idiomatic React Testing Patterns

Testing React components seems simple at first. Then you need to test something that isn't a pure interaction and things seem to break down. These 4 patterns should help you write readable, flexible tests for the type of component you are testing.


I recommend doing all setup in the most functional way possible. If you can avoid it, don't set variables in a beforeEach. This will help ensure tests are isolated and make things a bit easier to reason about. I use a pattern that gives great defaults for each test example but allows every example to override props when needed:


Creating a redis Module in 15 lines of code!

A quick guide to write a very very simple "ECHO" style module to redis and load it. It's not really useful of course, but the idea is to illustrate how little boilerplate it takes.

Step 1: open your favorite editor and write/paste the following code in a file called module.c

#include "redismodule.h"
/* ECHO <string> - Echo back a string sent from the client */
int EchoCommand(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
spaze /
Last active July 5, 2023 11:29
Opera VPN behind the curtains is just a proxy, here's how it works

2023 update

ℹ️ Please note this research is from 2016 when Opera has first added their browser "VPN", even before the "Chinese deal" was closed. They have since introduced some real VPN apps but this below is not about them.

🕵️ Some folks also like to use this article to show a proof that the Opera browser is a spyware or that Opera sells all your data to 3rd parties or something like that. This article here doesn't say anything like that.

When setting up (that's immediately when user enables it in settings) Opera VPN sends few API requests to to obtain credentials and proxy IPs, see below, also see The Oprah Proxy.

The browser then talks to a proxy (when VPN location is set to Germany), it's IP address can only be resolved from within Opera when VPN is on, it's (or similar, see below). It's an HTTP/S proxy which requires auth.

rauchg /
Last active September 22, 2023 13:57
dmvaldman /
Last active November 3, 2021 08:54
Promises as EventEmitters

The issue: browsers will wait approximately 300ms from the time that you tap the button to fire the click event. The reason for this is that the browser is waiting to see if you are actually performing a double tap.

(from a new defunct article)

touch-action CSS property can be used to disable this behaviour.

touch-action: manipulation The user agent may consider touches that begin on the element only for the purposes of scrolling and continuous zooming. Any additional behaviors supported by auto are out of scope for this specification.

View usable-promises.js
// from the brilliant mind of sb
var _catch = Promise.prototype.catch;
Promise.prototype.catch = function () {
return, function (err) { setTimeout(function () { throw(err); }, 0); });
Avaq / combinators.js
Last active September 11, 2023 08:24
Common combinators in JavaScript
View combinators.js
const I = x => x
const K = x => y => x
const A = f => x => f (x)
const T = x => f => f (x)
const W = f => x => f (x) (x)
const C = f => y => x => f (x) (y)
const B = f => g => x => f (g (x))
const S = f => g => x => f (x) (g (x))
const S_ = f => g => x => f (g (x)) (x)
const S2 = f => g => h => x => f (g (x)) (h (x))
View runtimer.js
function* runTimer(getState) {
while(yield take('START')) {
while(true) {
const {stop, tick} = yield race({
stop : take('STOP'),
tick : call(wait, ONE_SECOND);
if ( !stop ) {
yield put(actions.tick());
View notes.js
// devDependencies in package.json:
"require-reload": "0.2.2",
"react-transform-hmr-no-accept": "1.0.1", // not published, get it here:
// in babelrc:
"env": {
"development": {
"plugins": [