@chasemoskal/magical

🪄 magical

web toolkit for lit apps

🕹️ live demo — magical.chasemoskal.com
📦 npm install @chasemoskal/magical
💖 made with open source love

magical is a collection of tools we build, maintain, and use every day to make great lit applications.

🤖 magic element

every magic element is also a lit element.

but magic elements have a realize method instead of a render method.

in your realize method, use this.use, to get access to a "hooks" interface for state management.

import {MagicElement, mixinCss, UseElement} from "@chasemoskal/magical"

import {html} from "lit"
import {property} from "lit/decorators.js"
import stylesCss from "./styles.css.js"

@mixinCss(stylesCss)
export class CounterElement extends MagicElement {

  @property({type: Number})
  start = 0

  realize() {
    const {use} = this
    const [count, setCount] = use.state(this.start)
    const increment = () => setCount(x => x + 1)

    use.setup(() => {
      const listener = () => console.log("resized")
      window.addEventListener("resize", listener)
      return () => window.removeEventListener("resize", listener)
    })

    return html`
      <div>
        <p>count ${count}</p>
        <button @click=${increment}>increment</button>
      </div>
    `
  }
}

there are some things to know about:

• you should never access use outside of realize
• like any hooks interface, your use calls must be in the same order every time
  • so don't put use.state or use.setup calls inside a for loop or in a callback function or anything like that
  • best practice is to keep use calls at the top-level
• use.state returns an array with four things:
  • the current value
  • the setter function
    • you can pass it a new value
    • or a function that takes the previous value and returns a new value
  • the getter function
    • the getter is useful getting the latest version of state in a callback
  • the previous value
    • you could compare current===previous to see if the value has changed
• use.setup
  • use this to run a setup routine every time the component connects to the dom
  • the setup function you provide should return a function that tears down and cleans up any mess, called when the component disconnects from the dom

✨ magic view

views have the same use hook interface, but views are not components or elements.

they're lit directives.

but like elements, views too can have a shadow dom, and their own css styles.

import {view} from "@chasemoskal/magical"

import {html} from "lit"
import stylesCss from "./styles.css.js"

export const CounterView = view({
    shadow: true,
    styles: stylesCss,
  }, use => (start: number) => {

  const [count, setCount] = use.state(start)
  const increment = () => setCount(x => x + 1)

  return html`
    <div>
      <p>count ${count}</p>
      <button @click=${increment}>increment</button>
    </div>
  `
})

the important thing to understand, is how they are used:

• views are used like this:

  // 🧐
  return html`
    <div>
      ${CounterView(2)}
    </div>
  `

  • this is great, because CounterView is fully typescript-typed
  • and it's directly imported, so it's easy to trace where views are being used (vscode find all references)
  • typescript will sniff out and complain about places you need to change when you update those parameters
• whereas using an element would be like this:

  // 🤮
  return html`
    <div>
      <counter-element start=2></counter-element>
    </div>
  `

  • this is OK for an html-only interface, but for real app development?
  • this sucks, no typescript typing
  • no imports, no vscode find all references
  • have to worry about dom registrations
  • views solve all of this

compared against elements:

• views are typescript functions, so their parameters are fully typed, vscode auto-refactoring works
• views are less cumbersome, because they don't need to be registered to the dom

compared against simple render functions:

• views have state
• views are independent rendering contexts
• views can have shadow dom and their own stylesheets

i think a good way to think about elements and views is like this:

• elements are entrypoints at the html-level
• most of our app features are implemented as views
• our views are comprised of simple render functions

📻 magic event

we have this handy helper for making custom dom events.

import {MagicEvent} from "@chasemoskal/magical"

export class ProfileChanged extends
  MagicEvent<{count: number}>("profile_changed") {}

// dispatch the event
MyCoolEvent
  .target(window)
  .dispatch({count: 1})

// listen for the event
const unlisten = MyCoolEvent
  .target(window)
  .listen(event => {
    console.log("profile changed", event.detail.count)
  })

instead of extending MagicEvent, you can just use ev directly to listen and dispatch custom events:

import {ev} from "@chasemoskal/magical"

ev(MyCustomEvent)
  .target(window)
  .dispatch({lol: "example"})

const unlisten = ev(MyCustomEvent)
  .target(window)
  .listen(event => {
    console.log("example event", event.detail.lol)
  })

🐫 camel css

we wanted sass-like css nesting, but in our web components.

so we built a parser and compiler for a new css language.

it can run serverside, as part of a build script, or our preferred method — live on the clientside, compiling stylesheets for our elements and views.

camel css can be a drop-in replacement for lit's css tagged-template function:

import {css} from "@chasemoskal/magical"

const styles = css`
div {
  p { color: red; }
}
`

camel-css uses ^ instead of sass's &

🪄 more magical tools

⚙️ registerElements and themeElements

for the love of god, if you're writing a web components library, do not call customElements.define in those component modules.

be polite, and allow us the opportunity to augment your elements, rename them, apply a css theme, and then we can register our augmented elements.

so, when we're making a library, we like to have a function like getElements that returns all the library's elements classes.

then it's easy for anybody to apply a css theme and register the elements:

import {registerElements, themeElements} from "@chasemoskal/magical"

registerElements(
  themeElements(
    themeCss,
    getElements(),
  )
)

• registerElements will automatically take CamelCaseComponent names and convert them into camel-case-component names

🎨 mixins for your lit elements

TODO documentation for these

• mixinCss
• mixinLightDom
• mixinRefreshInterval
• mixinContextRequired

🏀 debounce

i've made like ten versions of this, and i think this is my masterpiece. it even has unit tests.

import {debounce} from "@chasemoskal/magical"

const action = () => console.log("action!")
const debouncedAction = debounce(1000, action)
// debouncedAction is a promise that resolves
// after the 1000 millseconds of no activity

debouncedAction()
debouncedAction()
await debouncedAction()
//> "action!"
// the action only fires once

this debouncer

• typescript
• works with functions or async functions
• returns promises
• the promises resolve with the actual value

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    💖 made with open source love