deka-dom-el/docs_src/p03-events.html.js

import { T, t } from "./utils/index.js";
export const info= {
	title: t`Events and Addons`,
	description: t`Using not only events in UI declaratively.`,
};

import { el } from "deka-dom-el";
import { simplePage } from "./layout/simplePage.html.js";
import { example } from "./components/example.html.js";
import { h3 } from "./components/pageUtils.html.js";
import { mnemonic } from "./components/mnemonic/events-init.js";
import { code } from "./components/code.html.js";
/** @param {string} url */
const fileURL= url=> new URL(url, import.meta.url);
const references= {
	mdn_listen: { /** element.addEventListener() */
		title: t`MDN documentation page for elemetn.addEventListener`,
		href: "https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener",
	},
	mdn_abortListener: { /** AbortSignal+element.addEventListener */
		title: t`MDN documentation page for using AbortSignal with element.addEventListener`,
		href: "https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener#signal",
	},
	web_events: { /** comparison listening options by WebReflection */
		href: "https://gist.github.com/WebReflection/b404c36f46371e3b1173bf5492acc944",
	},
	mdn_customElement: { /** Custom Element lifecycle callbacks */
		href: "https://developer.mozilla.org/en-US/docs/Web/API/Web_components/Using_custom_elements#custom_element_lifecycle_callbacks" 
	},
	mdn_mutation: { /** MutationObserver */
		href: "https://developer.mozilla.org/en-US/docs/Web/API/MutationObserver",
	},
	vue_fix: { /** Readding the element to the DOM fix by Vue */
		title: t`Vue and Web Components, lifecycle implementation readding the element to the DOM`,
		href: "https://vuejs.org/guide/extras/web-components.html#lifecycle",
	}
};
/** @param {import("./types.d.ts").PageAttrs} attrs */
export function page({ pkg, info }){
	const page_id= info.id;
	return el(simplePage, { info, pkg }).append(
		el("h2", t`Listenning to the native DOM events and other Addons`),
		el("p").append(...T`
			We quickly introduce helper to listening to the native DOM events. And library syntax/pattern so-called
			${el("em", t`Addon`)} to incorporate not only this in UI templates declaratively.
		`),
		
		el(code, { src: fileURL("./components/examples/events/intro.js"), page_id }),
		
		el(h3, t`Events and listenners`),
		el("p").append(...T`
			In JavaScript you can listen to the native DOM events of the given element by using
			${el("a", references.mdn_listen).append( el("code", "element.addEventListener(type, listener, options)") )}.
			The library provides an alternative (${el("code", "on")}) accepting the differen order of the arguments:
		`),
		el(example, { src: fileURL("./components/examples/events/compare.js"), page_id }),
		el("p").append(...T`
			…this is actually one of the two differences. The another one is that ${el("code", "on")} accepts only
			object as the ${el("code", "options")} (but it is still optional).
		`),
		el("p", { className: "notice" }).append(...T`
			The other difference is that there is ${el("strong", "no")} ${el("code", "off")} function. You can remove
			listener declaratively using ${el("a", { textContent: "AbortSignal", ...references.mdn_abortListener })}:
		`),
		el(example, { src: fileURL("./components/examples/events/abortSignal.js"), page_id }),
		el("div", { className: "notice" }).append(
			el("p", t`So, there are (typically) three ways to handle events. You can use:`),
			el("ul").append(
				el("li").append( el("code", `el("button", { textContent: "click me", "=onclick": "console.log(event)" })`)),
				el("li").append( el("code", `el("button", { textContent: "click me", onclick: console.log })`)),
				el("li").append( el("code", `el("button", { textContent: "click me" }, on("click", console.log))`))
			),
			el("p").append(...T`
				In the first example we force to use HTML attribute (it corresponds to
				${el("code", `<button onclick="console.log(event)">click me</button>`)}). ${el("em", t`Side note:
				this can be useful in case of SSR.`)} To study difference, you can read a nice summary here:
				${el("a", { textContent: "GIST @WebReflection/web_events.md", ...references.web_events })}.
			`)
		),

		el(h3, t`Addons`),
		el("p").append(...T`
			From practical point of view, ${el("em", t`Addons`)} are just functions that accept any HTML element as
			their first parameter. You can see that the ${el("code", "on(…)")} fullfills this requirement.
		`),
		el("p").append(...T`
			You can use Addons as ≥3rd argument of ${el("code", "el")} function. This way is possible to extends your
			templates by additional (3rd party) functionalities. But for now mainly, you can add events listeners:
		`),
		el(example, { src: fileURL("./components/examples/events/templateWithListeners.js"), page_id }),
		el("p").append(...T`
			As the example shows, you can also provide types in JSDoc+TypeScript by using global type
			${el("code", "ddeElementAddon")}. Also notice, you can use Addons to get element reference.
		`),
		el(h3, t`Life-cycle events`),
		el("p").append(...T`
			Addons are called immediately when the element is created, even it is not connected to live DOM yet.
			Therefore, you can understand the Addon to be “oncreate” event.
		`),
		el("p").append(...T`
			The library provide three additional live-cycle events corresponding to how they are named in a case of
			custom elements: ${el("code", "on.connected")}, ${el("code", "on.disconnected")} and ${el("code", "on.attributeChanged")}.
		`),
		el(example, { src: fileURL("./components/examples/events/live-cycle.js"), page_id }),
		el("p").append(...T`
			For Custom elements, we will later introduce a way to replace ${el("code", "*Callback")} syntax with
			${el("code", "dde:*")} events. The ${el("code", "on.*")} functions then listen to the appropriate
			Custom Elements events (see ${el("a", { textContent: t`Custom element lifecycle callbacks | MDN`, ...references.mdn_customElement })}).
		`),
		el("p").append(...T`
			But, in case of regular elemnets the ${el("a", references.mdn_mutation).append(el("code", "MutationObserver"), " | MDN")}
			is internaly used to track these events. Therefore, there are some drawbacks:
		`),
		el("ul").append(
			el("li").append(...T`
				To proper listener registration, you need to use ${el("code", "on.*")} not \`on("dde:*", …)\`!
			`),
			el("li").append(...T`
				Use sparingly! Internally, library must loop of all registered events and fires event properly.
				${el("strong", t`It is good practice to use the fact that if an element is removed, its children are
				also removed!`)} In this spirit, we will introduce later the ${el("strong", t`host`)} syntax to
				register, clean up procedures when the component is removed from the app.
			`),
		),
		el("p").append(...T`
			To provide intuitive behaviour, similar also to how the life-cycle events works in other
			frameworks/libraries, deka-dom-el library ensures that ${el("code", "on.connected")} and
			${el("code", "on.disconnected")} are called only once and only when the element, is (dis)connected to
			live DOM. The solution is inspired by ${el("a", { textContent: "Vue", ...references.vue_fix })}. For using
			native behaviour re-(dis)connecting element, use:
		`),
		el("ul").append(
			el("li").append(...T`custom ${el("code", "MutationObserver")} or logic in (dis)${el("code", "connectedCallback")} or…`),
			el("li").append(...T`re-add ${el("code", "on.connected")} or ${el("code", "on.disconnected")} listeners.`)
		),

		el(h3, t`Final notes`),
		el("p", t`The library also provides a method to dispatch the events.`),
		el(example, { src: fileURL("./components/examples/events/compareDispatch.js"), page_id }),
		
		el(mnemonic)
	);
}