Memo/reuse in O.el (#18)

* 🎉

* ✨ Add hasOwn helper and replace `Reflect.*`

* Update package.json

examples/components/todosComponent.js

@@ -16,10 +16,12 @@ const className= style.host(todosComponent).css`
 `;
 /** @param {{ todos: string[] }} */
 export function todosComponent({ todos= [ "Task A" ] }= {}){
-	const todosO= O(todos.map(t=> O(t)), {
-		add(v){ this.value.push(O(v)); },
-		remove(i){ O.clear(this.value.splice(i, 1)[0]); }
+	let key= 0;
+	const todosO= O(new Map(), {
+		add(v){ this.value.set(key++, O(v)); },
+		remove(key){ O.clear(this.value.get(key)); this.value.delete(key); }
 	});
+	todos.forEach(text=> O.action(todosO, "add", text));
 
 	const name= "todoName";
 	const onsubmitAdd= on("submit", event=> {
@@ -31,24 +33,16 @@ export function todosComponent({ todos= [ "Task A" ] }= {}){
 	const onremove= on("remove", event=>
 		O.action(todosO, "remove", event.detail));
 	
-	const ul_todos_version= 1; // ul_todos_v1/ul_todos_v2
-	const ul_todos_v1= el("ul").append(
-		O.el(todosO, ts=> ts
-			.map((textContent, value)=>
-				el(todoComponent, { textContent, value, className }, onremove))
-	));
-	const ul_todos_v2= ts=> el("ul").append(
-		...ts.map((textContent, value)=>
-			el(todoComponent, { textContent, value, className }, onremove))
-	);
-	
 	return el("div", { className }).append(
 		el("div").append(
 			el("h2", "Todos:"),
 			el("h3", "List of todos:"),
-			O.el(todosO, ts=> !ts.length
+			O.el(todosO, (ts, memo)=> !ts.size
 				? el("p", "No todos yet")
-				: ( !(ul_todos_version-1) ? ul_todos_v1 : ul_todos_v2(ts) )
+				: el("ul").append(
+					...Array.from(ts).map(([ value, textContent ])=>
+						memo(value, ()=> el(todoComponent, { textContent, value, className }, onremove)))
+				)
 			),
 			el("p", "Click to the text to edit it.")
 		),
@@ -61,7 +55,7 @@ export function todosComponent({ todos= [ "Task A" ] }= {}){
 		),
 		el("div").append(
 			el("h3", "Output (JSON):"),
-			el("output", O(()=> JSON.stringify(todosO, null, "\t")))
+			el("output", O(()=> JSON.stringify(Array.from(todosO()), null, "\t")))
 		)
 	)
 }

package.json

@@ -79,7 +79,7 @@
 		},
 		{
 			"path": "./index-with-observables.js",
-			"limit": "5 kB"
+			"limit": "5.25 kB"
 		}
 	],
 	"modifyEsbuildConfig": {

src/dom.js

@@ -65,12 +65,13 @@ export function createElement(tag, attributes, ...addons){
 	scoped= 2;
 	return el;
 }
+import { hasOwn } from "./helpers.js";
 /** @param {HTMLElement} element @param {HTMLElement} [root] */
 export function simulateSlots(element, root= element, mapper= undefined){
 	const _default= Symbol.for("default");
 	const slots= Array.from(root.querySelectorAll("slot"))
 		.reduce((out, curr)=> Reflect.set(out, curr.name || _default, curr) && out, {});
-	const has_d= Reflect.has(slots, _default);
+	const has_d= hasOwn(slots, _default);
 	element.append= new Proxy(element.append, {
 		apply(orig, _, els){
 			if(!els.length) return element;
@@ -198,7 +199,7 @@ export function elementAttribute(element, op, key, value){
 import { isUndef } from "./helpers.js";
 //TODO add cache? `(Map/Set)<el.tagName+key,isUndef>`
 function isPropSetter(el, key){
-	if(!Reflect.has(el, key)) return false;
+	if(!(key in el)) return false;
 	const des= getPropDescriptor(el, key);
 	return !isUndef(des.set);
 }

src/helpers.js

@@ -1,3 +1,4 @@
+export const hasOwn= (...a)=> Object.prototype.hasOwnProperty.call(...a);
 export function isUndef(value){ return typeof value==="undefined"; }
 export function typeOf(v){
 	const t= typeof v;
@@ -19,7 +20,7 @@ export function observedAttributes(instance, observedAttribute){
 	const { observedAttributes= [] }= instance.constructor;
 	return observedAttributes
 		.reduce(function(out, name){
-			Reflect.set(out, kebabToCamel(name), observedAttribute(instance, name));
+			out[kebabToCamel(name)]= observedAttribute(instance, name);
 			return out;
 		}, {});
 }

src/observables-lib.js

@@ -1,7 +1,8 @@
 export const mark= "__dde_observable";
+import { hasOwn } from "./helpers.js";
 
 export function isObservable(candidate){
-	try{ return Reflect.has(candidate, mark); }
+	try{ return hasOwn(candidate, mark); }
 	catch(e){ return false; }
 }
 /** @type {function[]} */
@@ -45,10 +46,10 @@ export function observable(value, actions){
 export { observable as O };
 observable.action= function(o, name, ...a){
 	const s= o[mark], { actions }= s;
-	if(!actions || !Reflect.has(actions, name))
+	if(!actions || !(name in actions))
 		throw new Error(`'${o}' has no action with name '${name}'!`);
 	actions[name].apply(s, a);
-	if(s.skip) return Reflect.deleteProperty(s, "skip");
+	if(s.skip) return (delete s.skip);
 	s.listeners.forEach(l=> l(s.value));
 };
 observable.on= function on(o, listener, options= {}){
@@ -65,11 +66,12 @@ observable.symbols= {
 };
 observable.clear= function(...observables){
 	for(const o of observables){
-		Reflect.deleteProperty(o, "toJSON");
 		const s= o[mark];
+		if(!s) continue;
+		delete o.toJSON;
 		s.onclear.forEach(f=> f.call(s));
 		clearListDeps(o, s);
-		Reflect.deleteProperty(o, mark);
+		delete o[mark];
 	}
 	function clearListDeps(o, s){
 		s.listeners.forEach(l=> {
@@ -89,24 +91,38 @@ const key_reactive= "__dde_reactive";
 import { enviroment as env } from "./dom-common.js";
 import { el } from "./dom.js";
 import { scope } from "./dom.js";
+// TODO: third argument for handle `cache_tmp` in re-render
 observable.el= function(o, map){
 	const mark_start= el.mark({ type: "reactive" }, true);
 	const mark_end= mark_start.end;
 	const out= env.D.createDocumentFragment();
 	out.append(mark_start, mark_end);
 	const { current }= scope;
+	let cache= {};
 	const reRenderReactiveElement= v=> {
-		if(!mark_start.parentNode || !mark_end.parentNode) // isConnected or wasn’t yet rendered
+		if(!mark_start.parentNode || !mark_end.parentNode) // === `isConnected` or wasn’t yet rendered
 			return removeObservableListener(o, reRenderReactiveElement);
+		const cache_tmp= cache; // will be reused in the useCache or removed in the while loop on the end
+		cache= {};
 		scope.push(current);
-		let els= map(v);
+		let els= map(v, function useCache(key, fun){
+			let value;
+			if(hasOwn(cache_tmp, key)){
+				value= cache_tmp[key];
+				delete cache_tmp[key];
+			} else
+				value= fun();
+			cache[key]= value;
+			return value;
+		});
 		scope.pop();
 		if(!Array.isArray(els))
 			els= [ els ];
-		let el_r= mark_start;
-		while(( el_r= mark_start.nextSibling ) !== mark_end)
-			el_r.remove();
 		mark_start.after(...els);
+		const el_last_keep= els[els.length-1];
+		let el_r;
+		while(( el_r= el_last_keep.nextSibling ) !== mark_end)
+			el_r.remove();
 		if(mark_start.isConnected)
 			requestCleanUpReactives(current.host());
 	};
@@ -183,7 +199,7 @@ function removeObservablesFromElements(o, listener, ...notes){
 				 * You can investigate the `__dde_reactive` key of the element.
 				 * */
 				element[key_reactive].forEach(([ [ o, listener ] ])=>
-					removeObservableListener(o, listener, o[mark]?.host() === element))
+					removeObservableListener(o, listener, o[mark] && o[mark].host && o[mark].host() === element))
 			)(element);
 		}
 		element[key_reactive].push([ [ o, listener ], ...notes ]);
@@ -216,7 +232,7 @@ function toObservable(o, value, actions, readonly= false){
 	const { onclear: ocs }= observable.symbols;
 	if(actions[ocs]){
 		onclear.push(actions[ocs]);
-		Reflect.deleteProperty(actions, ocs);
+		delete actions[ocs];
 	}
 	const { host }= scope;
 	Reflect.defineProperty(o, mark, {