Eugene Samonenko ambroseus

Advanced memoization and effects in React

Memoization is a somewhat fraught topic in the React world, meaning that it's easy to go wrong with it, for example, by [making memo() do nothing][memo-pitfall] by passing in children to a component. The general advice is to avoid memoization until the profiler tells you to optimize, but not all use cases are general, and even in the general use case you can find tricky nuances.

Discussing this topic requires some groundwork about the technical terms, and I'm placing these in once place so that it's easy to skim and skip over:

Memoization means caching the output based on the input; in the case of functions, it means caching the return value based on the arguments.
Values and references are unfortunately overloaded terms that can refer to the low-level implementation details of assignments in a language like C++, for example, or to memory allocation (i.e., value and reference types in C#), but that should just be ignored in JavaScript, because "pass b

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.

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

	module.exports = getVariants

	function getVariants(str = '', symbol = '.') {
	const bitsLength = str.length - 1
	const maxVariants = 2 ** bitsLength
	const chars = str.split('')

	const reverseBits = (value) =>
	value.toString(2).padStart(bitsLength, '0').split('').reverse().map(Number)

	module.exports = getVariants

	function getVariants(str = '', symbol = '.') {
	const variants = [str]
	const bitsLength = str.length - 1

	if (bitsLength === -1) {
	return []
	}

	function getCSSPath(node, optimized) {
	const ELEMENT_NODE = 1
	const DOCUMENT_NODE = 9

	if (node.nodeType !== ELEMENT_NODE) return ''

	const steps = []
	let contextNode = node

	while (contextNode) {

	const useApi = (apiFactory, initialState) => {
	let [state, setState] = useState(initialState);
	return useMemo(() => apiFactory({ state, setState }), [
	state,
	setState,
	apiFactory
	]);
	};

	const createStore = (apiFactory, initialState) => {

	btn.addEventListener("send-btn",onSend);
	send = CAF(send);
	var prevSend = Promise.resolve();

	function onSend(evt) {
	prevSend.finally(function f(){
	prevSend = send(
	CAF.timeout(1000,"send took too long."),
	{ some: "data" }
	)

	# to generate your dhparam.pem file, run in the terminal
	openssl dhparam -out /etc/nginx/ssl/dhparam.pem 2048