jaabiri salim jaabiri

Iterables, AsyncIterables, Observables, Oh My!

I know there is a lot of confusion around Observables, Iterables, AsyncIterables and AsyncObservables. Let's try to break this down and the reasons for each.

Pull versus Push Collections

When it comes to collections, you have two ways of thinking about collections, push versus pull. With pull, the consumer is in control of when you get the items, but with push, you get the values when the producer is ready.

Pull Based Collections

useSubscription and useMutableSource¹ tearing and deopt behavior.

Mounting a new tree

The tree below represents a React application mounting. During mount, two components read from an external, mutable source. The first one (List) reads version 1 of that data and the second one (Item) reads version 2.

Deopt

`useSubscription` (legacy mode)

N/A.

I heard some points of criticism to how React deals with reactivity and it's focus on "purity". It's interesting because there are really two approaches evolving. There's a mutable + change tracking approach and there's an immutability + referential equality testing approach. It's difficult to mix and match them when you build new features on top. So that's why React has been pushing a bit harder on immutability lately to be able to build on top of it. Both have various tradeoffs but others are doing good research in other areas, so we've decided to focus on this direction and see where it leads us.

I did want to address a few points that I didn't see get enough consideration around the tradeoffs. So here's a small brain dump.

"Compiled output results in smaller apps" - E.g. Svelte apps start smaller but the compiler output is 3-4x larger per component than the equivalent VDOM approach. This is mostly due to the code that is usually shared in the VDOM "VM" needs to be inlined into each component. The tr

Everything I Know About UI Routing

Definitions

Location - The location of the application. Usually just a URL, but the location can contain multiple pieces of information that can be used by an app
1. pathname - The "file/directory" portion of the URL, like invoices/123
2. search - The stuff after ? in a URL like /assignments?showGrades=1.
3. query - A parsed version of search, usually an object but not a standard browser feature.
4. hash - The # portion of the URL. This is not available to servers in request.url so its client only. By default it means which part of the page the user should be scrolled to, but developers use it for various things.
5. state - Object associated with a location. Think of it like a hidden URL query. It's state you want to keep with a specific location, but you don't want it to be visible in the URL.

	import { GeomUtils, TLCursor } from '@tldraw/core'
	import * as React from 'react'

	function getCursorCss(svg: string, r: number, f = false) {
	return (
	`url("data:image/svg+xml,<svg height='32' width='32' viewBox='0 0 35 35' xmlns='http://www.w3.org/2000/svg'><g fill='none' style='transform-origin:center center' transform='rotate(${r})${
	f ? ` scale(-1,-1) translate(0, -32)` : ''
	}'>` +
	svg.replaceAll(`"`, `'`) +
	'</g></svg>") 16 16, pointer'

	function useAbortController() {
	const abortControllerRef = React.useRef()
	const getAbortController = React.useCallback(() => {
	if (!abortControllerRef.current) {
	abortControllerRef.current = new AbortController()
	}
	return abortControllerRef.current
	}, [])

	React.useEffect(() => {

	import React from 'react'

	export default function useDarkMode({
	intervalTime = 300,
	getIsDark = defaultGetIsDark,
	} = {}) {
	// Keep track of the current mode
	const [isDark, setIsDark] = React.useState(() => getIsDark())

	// Set up the checker

	/**
	* VISUALLY HIDDEN
	* Hides element visually and removes it from the flow,
	* but importantly, allows assitive technology to access it
	*/
	.visually-hidden {
	border: 0;
	clip: rect(0 0 0 0);
	height: auto;
	margin: 0;

	// Index.html
	<div>
	<h1>File upload</h1>
	<input type="file" multiple onChange={e => uploadFile(e)}/>
	</div>


	// Index.js
	const uploadFile = async e => {
	const files = e.target.files

	import { useEffect, useRef } from 'react';

	function getItem(storage, key) {
	const value = storage.getItem(key);

	if (!value) return null;

	try {
	return JSON.parse(value);
	} catch (error) {