mirror of
https://github.com/jaandrle/deka-dom-el
synced 2024-11-21 23:39:37 +01:00
76 lines
3.5 KiB
JavaScript
76 lines
3.5 KiB
JavaScript
import { simplePage } from "./layout/simplePage.html.js";
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import { el } from "deka-dom-el";
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import { example } from "./components/example.html.js";
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import { h3 } from "./components/pageUtils.html.js";
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/** @param {string} url */
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const fileURL= url=> new URL(url, import.meta.url);
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/** @param {import("./types.d.ts").PageAttrs} attrs */
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export function page({ pkg, info }){
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const page_id= info.id;
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return el(simplePage, { info, pkg }).append(
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el("h2", "Using signals to manage reactivity"),
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el("p").append(
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"How a program responds to variable data or user",
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" interactions is one of the fundamental problems of programming.",
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" If we desire to solve the issue in a declarative manner,",
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" signals may be a viable approach.",
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),
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el(example, { src: fileURL("./components/examples/signals/intro.js"), page_id }),
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el(h3, "Introducing signals"),
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el("p").append(
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"Using signals, we split program logic into the three parts.",
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" Firstly (α), we create a variable (constant) representing reactive",
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" value. Somewhere later, we can register (β) a logic reacting",
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" to the signal value changes. Similarly, in a remaining part (γ), we",
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" can update the signal value."
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),
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el("p").append(
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"All this is just an example of ",
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el("a", { textContent: "Event-driven programming", href: "https://en.wikipedia.org/wiki/Event-driven_programming", title: "Wikipedia: Event-driven programming" }),
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" and ",
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el("a", { textContent: "Publish–subscribe pattern", href: "https://en.wikipedia.org/wiki/Publish%E2%80%93subscribe_pattern", title: "Wikipedia: Publish–subscribe pattern" }),
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" (compare for example with ", el("a", { textContent: "fpubsub library", href: "https://www.npmjs.com/package/fpubsub", title: "NPM package: fpubsub" }), ").",
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" All three parts can be in some manner independent and still connected",
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" to the same reactive entity."
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),
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el("p").append(
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"Signals are implemented in the library as functions. To see current value",
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" of signal, just call it without any arguments ", el("code", "console.log(signal())"), ".",
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" To update the signal value, pass any argument ", el("code", "signal('a new value')"), ".",
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" For listenning the signal value changes, use ", el("code", "S.on(signal, console.log)"), "."
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),
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el("p").append(
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"Similarly to the ", el("code", "on"), " function to register DOM events listener.",
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" You can use ", el("code", "AbortController"), "/", el("code", "AbortSignal"), " to",
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" ", el("em", "off"), "/stop listenning. For representing “live” piece of code computation pattern:"
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),
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el(example, { src: fileURL("./components/examples/signals/computations-abort.js"), page_id }),
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el("div", { className: "notice" }).append(
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el("p", "Mnemonic"),
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el("ul").append(
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el("li").append(
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el("code", "S(<value>)"), " — signal: reactive value",
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),
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el("li").append(
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el("code", "S(()=> <computation>)"), " — signal: reactive value dependent on calculation using other signals",
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),
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el("li").append(
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el("code", "S.on(<signal>, <listener>[, <options>])"), " — listen to the signal value changes",
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),
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el("li").append(
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el("code", "S.clear(...<signals>)"), " — off and clear signals",
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),
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el("li").append(
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el("code", "S(<value>, <actions>)"), " — signal: pattern to create complex reactive objects/arrays",
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),
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el("li").append(
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el("code", "S.action(<signal>, <action-name>, ...<action-arguments>)"), " — invoke an action for given signal"
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)
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)
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),
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);
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}
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