@benev/slate

🪨 @benev/slate

🚧 prerelease wip under constructon subject to change

• frontend ui framework, built on lit
• wonderful web components
• versatile views
• hipster hooks syntax
• satisfying state management
• useful utilities
• top-tier typescript typings

most devs misunderstand how to leverage web components.

you're not supposed to make your whole app out of web components.
they're too cumbersome — web components are html-native, not typescript-native — so they don't take typesafe props, they're referred to by html tag names with poor ide support, and juggling their dom registrations is a pain.

this is why views are important, and are a central feature of slate — views are almost the same as components (they can use shadow-dom), except that views are ergonomically handled via javascript, they accept props, they don't need registration (they're simply imported) — and views enjoy full typescript typings.

you want to think of web components as the tip of your iceberg — they are the entrypoints to your ui — they are the universal control surfaces to help html authors interact with your systems — but below the surface, most of your internals can be made of easily-composable views.

👷 quick start

1. install slate

   npm i @benev/slate
   

2. create your app's nexus
   you'll use the nexus to create components and views which have hard-wired access to your context object.

   import {Nexus, Context} from "@benev/slate"
   
   export const nexus = new Nexus(
     new class extends Context {
   
       // this theme is applied to all your components and views
       theme = css`
         * {
           margin: 0;
           padding: 0;
           box-sizing: border-box;
         }
       `
   
       // add app-level stuff you'd like to make widely available
       my_cool_thing = {my_awesome_data: 123}
     }
   )
   

3. import templating functions
   these are augmented versions of lit's templating functions, which directly implement signals.
   they are fully compatible with lit.

   import {html, css, svg} from "@benev/slate"
   

⚙️ components

you can create custom html elements that work in plain html or any web framework.

nexus.shadow_component

export const MyShadowComponent = nexus.shadow_component(use => {
  use.styles(css`span {color: yellow}`)
  const count = use.signal(0)
  const increment = () => count.value++

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

nexus.light_component

export const MyLightComponent = nexus.light_component(use => {
  const count = use.signal(0)
  const increment = () => count.value++

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

deploying your components

• register components to the dom

  import {register_to_dom} from "@benev/slate"
  
  register_to_dom({
    MyShadowComponent,
    MyLightComponent,
  })
  

• now use your components via html

  <section>
    <my-shadow-component></my-shadow-component>
    <my-light-component></my-light-component>
  </section>
  

🖼️ views

views are just like components, but are not registered to the dom as custom html elements.
instead, they are used via javascript.
you import them, and inject them into your lit-html templates.
they accept js parameters called props, and are fully typescript-typed.

nexus.shadow_view

export const MyShadowView = nexus.shadow_view(use => (start: number) => {
  use.name("my-shadow-view")
  use.styles(css`span {color: yellow}`)
  const count = use.signal(start)
  const increment = () => count.value++

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

• auto_exportparts is enabled by default.
  • auto exportparts is an experimental shadow_view feature that makes it bearable to use the shadow dom extensively.
  • if auto_exportparts is enabled, and you provide the view a part attribute, then it will automatically re-export all internal parts, using the part as a prefix.
  • thus, parts can bubble up: each auto_exportparts shadow boundary adds a new hyphenated prefix, so you can do css like ::part(search-input-icon).

nexus.light_view

export const MyLightView = nexus.light_view(use => (start: number) => {
  use.name("my-light-view")
  const count = use.signal(start)
  const increment = () => count.value++

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

deploying your views

• using a shadow view

  html`<div>${MyShadowView([123])}</div>`
  

  • shadow views need their props wrapped in an array
  • shadow views will accept a settings object

    html`
      <div>
        ${MyShadowView([123], {
          content: html`<p>slotted content</p>`,
          auto_exportparts: true,
          attrs: {part: "cool", "data-whatever": true},
        })}
      </div>
    `
    

• using a light view

  html`<div>${MyLightView(123)}</div>`
  

  • light views are beautifully simple
  • they just take props as arguments
  • without any shadow-dom, they have no stylesheet, and without a wrapping element, they have no attributes
• note
  • all views are rendered into a <slate-view view="my-name"> component

🪝 use hooks — for views and components

slate's hooks have the same rules as any other framework's hooks: the order that hooks are executed in matters, so you must not call hooks under an if statement or in any kind of for loop or anything like that.

core hooks

• use.name ~ shadow_view, light_view
  assign a stylesheet to the shadow root.
  only works on views, because having a name to differentiate views is handy (components have the names they were registered to the dom with).

  use.name("my-cool-view")
  

• use.styles ~ shadow_view, shadow_component
  assign a stylesheet to the shadow root.
  only works on shadow views or components (light views/components are styled from above).

  use.styles(css`span { color: yellow }`)
  

• use.state
  works like react useState hook.
  we actually recommend using signals instead (more on those later).

  const [count, setCount] = use.state(0)
  const increment = () => setCount(count + 1)
  

• use.once
  initialize a value once

  const random_number = use.once(() => Math.random())
  

• use.mount
  perform setup/cleanup on dom connected/disconnected

  use.mount(() => {
    const interval = setInterval(increment, 1000)
    return () => clearInterval(interval)
  })
  

• use.init
  perform a setup/cleanup, but also return a value

  const scene = use.init(() => {
  
    // called whenever dom is connected
    const scene = setup_3d_scene_for_example()
  
    return [
      scene, // value returned
      () => scene.cleanup(), // cleanup called on dom disconnect
    ]
  })
  

• use.defer
  execute a function everytime a render finishes.
  you might want to do this if you need to query for elements you just rendered.

  use.defer(() => {
    const div = document.querySelector("div")
    const rect = div.getBoundingClientRect()
    report_rect(rect)
  })
  

signal hooks

• use.signal
  create a reactive container for a value (inspired by preact signals)

  const count = use.signal(0)
  const increment = () => count.value++
  

  you can directly inject the whole signal into html

  html`<span>${count}</span>`
  

• use.computed create a signal that is derived from other signals

  const count = use.signal(2)
  const tripled = use.computed(() => count.value * 3)
  console.log(tripled.value) //> 6
  

• use.op
  create an OpSignal in a loading/error/ready state, and it can hold a result value

  const count = use.op()
  count.load(async() => fetchCount("/count"))
  

flatstate hooks

• use.flatstate
  create a reactive object (inspired by mobx and snapstate)

  const state = use.flatstate({count: 0})
  const increment = () => state.count++
  

watch hooks

• use.watch
  rerender when anything under part of a StateTree is changed.
  todo: document how this works via watch.stateTree({}).

  const whatever = use.watch(() => use.context.state.whatever)
  

useful accessors

these are not hooks, just access to useful things you may need, so you're allowed to use them under if statements or whatever.

• use.context
  access to your app's context, for whatever reason

  // access your own things on the context
  use.context.my_cool_thing
  

• use.element access the underlying html element

  use.element.querySelector("p")
  

• use.shadow ~ shadow_view, shadow_component
  access to the shadow root

  use.shadow.querySelector("slot")
  

• use.attrs ~ shadow_component, light_component
  declare accessors for html attributes

  const attrs = use.attrs({
    start: Number,
    label: String,
    ["data-active"]: Boolean,
  })
  

  set them like normal js properties

  attrs.start = 123
  attrs.label = "hello"
  attrs["data-active"] = true
  

  get them like normal js properties

  console.log(attrs.start) // 123
  console.log(attrs.label) // "hello"
  console.log(attrs["data-active"]) // true
  

  components rerender when any attributes change from outside

🥇 plain elements — gold and silver

gold and silver are "plain" elements, which are alternatives to LitElement.
they're used as primitives underlying nexus components.
for most cases you probably want to stick with the nexus components, and only use gold/silver when you're doing some funky sorcery, or you yearn to go back to a simpler time without hooks.

consider these imports for the following examples:

import {GoldElement, SilverElement, attributes, flat} from "@benev/slate"

gold element — shadow-dom element

export class MyGold extends GoldElement {
  static get styles() { return css`span {color: blue}` }

  #attrs = attributes(this as GoldElement, {
    label: String
  })

  #state = flat.state({
    count: 0,
  })

  render() {
    return html`
      <span>${this.#state.count}</span>
      <button @click=${() => this.#state.count++}>
        ${this.#attrs.label}
      </button>
    `
  }
}

silver element — light-dom element

export class MySilver extends SilverElement {

  #attrs = attributes(this as SilverElement, {
    label: String
  })

  #state = flat.state({
    count: 0,
  })

  render() {
    return html`
      <span>${this.#state.count}</span>
      <button @click=${() => this.#state.count++}>
        ${this.#attrs.label}
      </button>
    `
  }
}

deploying plain elements

if you want plain elements to have reactivity or have the context's css theme applied, you'll want to run them through nexus.components before you register them:

register_to_dom({
  ...nexus.components({
    MyGold,
    MySilver,
  }),
})

🔮 deferred context

you can extend the context with anything you'd like to make easily available to your components and views:

export const nexus = new Nexus(
  new class extends Context {
    my_cool_thing = {my_awesome_data: 123}
  }
)

but since your components are importing nexus, the above example creates the context at import-time.

you may instead prefer to defer the creation of your context until later, at run-time:

// define your context class
export class MyContext extends Context {
  my_cool_thing = {my_awesome_data: 123}
}

// create nexus *without yet* instancing the context
export const nexus = new Nexus<MyContext>()

//
// ... later in another file,
// maybe in your main.ts ...
//

// instance and assign your context, now, at runtime
nexus.context = new MyContext()

// just be sure to assign context *before* you register your components
register_to_dom(myComponents)

🛠️ standalone utilities

if you're using nexus components and views, you'll probably be using these utilities via the use hooks, which will provide a better developer experience.

however, the following utilities are little libraries in their own right, and can be used in a standalone capacity.

🛎️ signals

signals are a simple form of state management.

this implementation is inspired by preact signals.

• signals — they hold values

  import {signal, signals} from "@benev/slate"
  
  const count = signal(0)
  const greeting = signal("hello")
  
  count.value++
  greeting.value = "bonjour"
  
  console.log(count.value) //> 1
  console.log(greeting.value) //> "bonjour"
  

• reaction — react when signals change

  signals.reaction(() => console.log("doubled", count.value * 2))
  //> doubled 2
  
  count.value = 2
  //> doubled 4
  

• html templating — you can omit .value

  html`<p>count is ${count}</p>`
  

• op signal — to represent async operations

  const json = signals.op<MyJson>()
  
  console.log(json.isLoading()) //> true
  
  await json.load(async() => {
    const data = await fetch_remote_data()
    return JSON.parse(data)
  })
  
  console.log(json.isReady()) //> true
  console.log(json.payload) //> {"your": "json data"}
  

• computed — signal derived from other signals

  count.value = 1
  
  const tripled = signals.computed(() => count.value * 3)
  
  console.log(tripled.value) //> 3
  

• wait — for debounced tracking

  const tripled = signals.computed(() => count.value * 3)
  console.log(tripled.value) //> 3
  
  count.value = 10
  console.log(tripled.value) //> 3 (too soon!)
  
  await signals.wait
  console.log(tripled.value) //> 30 (there we go)
  

• signal tower

  import {SignalTower} from "@benev/slate"
  
  const signals = new SignalTower()
  

  • slate comes with a default tower called signals, but you can create your own
  • signal towers are completely separated from one another

🥞 flatstate

flatstate help you create state objects and react when properties change.

flatstate is inspired by mobx and snapstate, but designed to be simpler. flatstate only works on flat state objects. only the direct properties of state objects are tracked for reactivity. this simplicity helps us avoid weird edge-cases or unexpected footguns.

flatstate basics

• make a flat state object

  import {flat} from "@benev/slate"
  
  const state = flat.state({count: 0})
  

• simple reaction

  flat.reaction(() => console.log(state.count))
  

  • flatstate immediately runs the function, and records which properties it reads
  • then, anytime one of those recorded properties changes, it runs your function again
  • your reaction can listen to more than one state object
• two-function reaction

  flat.reaction(
  
    // your "collector" function
    () => ({count: state.count}),
  
    // your "responder" function
    ({count}) => console.log(count),
  )
  

  • now there's a separation between your "collector" and your "responder"
  • the collector "passes" relevant data to the responder function
  • flatstate calls the responder whenever that data changes
• stop a reaction

  const stop = flat.reaction(() => console.log(state.count))
  
  stop() // end this particular reaction
  

• reactions are debounced -- so you may have to wait to see state changes

  const state = flat.state({amount: 100})
  
  state.amount = 101
  console.log(state.amount) //> 100 (old value)
  
  await flat.wait
  console.log(state.amount) //> 101 (now it's ready)
  

flatstate advanced

• create readonly access to a state object

  const state = flat.state({count: 0})
  const rstate = Flat.readonly(state)
  
  state.count = 1
  await flat.wait
  console.log(rstate.count) //> 1
  
  rstate.count = 2 // !! ReadonlyError !!
  

  • btw, you can use readonly on anything, not just flatstate
• multiple flatstate instances are totally isolated from each other

  const flat1 = new Flat()
  const flat2 = new Flat()
  

flatstate integration with frontend elements

• let your components rerender on flat state changes

  import {apply} from "@benev/slate"
  
  const MyElement2 = mixin.flat(flat)(MyElement)
    // can also be a class decorator
  
  const elements2 = apply.flat(flat)(elements)
  

  • this works on any BaseElement, which includes LitElement, GoldElement, SilverElement, ShadowView, and LightView

☢️ reactor

create reactions that listen to both signals and flatstates at the same time.

signals and flat both share the same reaction syntax, but they are separate state management systems. reactor lets you combine both.

• you can use one-function reaction syntax:

  import {reactor, flatstate, signal} from "@benev/slate"
  
  const state = state({count: 0})
  const count = signal(0)
  
  // use the reactor to setup a reaction
  reactor.reaction(() => console.log(`
    flat count is ${state.count},
    signal count is ${count.value}
  `))
  

• two-function reaction syntax:

  reactor.reaction(
    () => ({a: state.count, b: count.value}),
    results => console.log(results),
  )
  

• reactions can be stopped:

  const stop = reactor.reaction(
    () => console.log(state.count)
  )
  
  // end this reaction
  stop()
  

• wait for the debouncer:

  await reactor.wait
  

💫 ops

utility for ui loading/error/ready states.

useful for implementing async operations that involve loading indicators.

you get a better dev-experience if you use ops via signals, but here is the documentation for plain ops on their own, without signals.

• create some ops

  import {Op} from "@benev/slate"
  
  Op.loading()
    //= {status: "loading"}
  
  Op.error("a fail occurred")
    //= {status: "error", reason: "a fail occurred"}
  
  Op.ready(123)
    //= {status: "ready", payload: 123}
  

• check an op's status (proper typescript type guards)

  Op.is.loading(op)
    //= false
  
  Op.is.error(op)
    //= false
  
  Op.is.ready(op)
    //= true
  

• grab an op's payload (undefined when not ready)

  const count = Op.ready(123)
  const loadingCount = Op.loading()
  
  Op.payload(count)
    //= 123
  
  Op.payload(loadingCount)
    //= undefined
  

• run an async operation which updates an op

  let my_op = Op.loading()
  
  await Op.load(
  
    // your setter designates which op to overwrite
    op => my_op = op,
  
    // your async function which returns the ready payload
    async() => {
      await nap(1000)
      return 123
    }
  )
  

• ops signals integration — we recommend using ops via signals.op() or use.op(), the OpSignal these return has nicer ergonomics

  const count = signals.op()
  
  // run an async operation
  await count.load(async() => {
    await sleep(1000)
    return 123
  })
  
  // check the status of this OpSignal
  count.isLoading() //= false
  count.isError() //= false
  count.isReady() //= true
  
  // grab the payload (undefined when not ready)
  count.payload //= 123
  
  // directly assign the op signal
  count.setLoading()
  count.setError("big fail")
  count.setReady(123)
  

🪈 pipe

• pipe data through a series of functions
• maybe you've done silly nesting like this:

  // bad
  register_to_dom(
    apply.signals(signals)(
      apply.flat(flat)(
        apply.css(theme)(
          requirement.provide(context)(elements)
        )
      )
    )
  )
  

• now you can do this instead:

  import {Pipe} from "@benev/slate"
  
  // good
  Pipe.with(elements)
    .to(requirement.provide(context))
    .to(apply.css(theme))
    .to(apply.flat(flat))
    .to(apply.signals(signals))
    .to(register_to_dom)
  

• call .done() when you want to return the result

🧐 more useful utils

no time to document these fully, but they're there

• debounce — is a pretty good debouncer
• deep — utilities for data structures like 'equal' and 'freeze'
• is — proper type guards
• explode_promise — make an inside-out promise
• generate_id — generate a crypto-random hexadecimal id string
• pub — easy pub/sub tool
• requirement — pass required data to a group of things