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Lit with css-in-js / https://gistcdn.githack.com/nexpr/bf2c22055484df1be3983c41e91128ef/raw/d1ac3aad5b750e8de1bf772a1cd7ad1bd964cfbd/index.html
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| import { html } from "lit" | |
| import { StylitElement } from "./StylitElement.js" | |
| class ExampleElement extends StylitElement { | |
| static properties = { | |
| n: {} | |
| } | |
| constructor() { | |
| super() | |
| this.n = 0 | |
| } | |
| render() { | |
| const $ = this.styleDirective | |
| return html` | |
| <div class=${$`border: 1px solid #aaa; :is(div) { padding: 10px }`}> | |
| <button @click=${() => this.n++}>${this.n}</button> | |
| <div class=${$`background: #ddd`}>text</div> | |
| ${this.n % 2 == 0 | |
| ? html`<div class=${$`color:red`}>text</div>` | |
| : html`<div class=${$`color:blue`}>text</div>` | |
| } | |
| <div class=${this.n % 2 === 0 ? $`color:red` : $`color:blue`}> | |
| text | |
| </div> | |
| <div class=${$`color:${this.n % 2 === 0 ? "red" : "blue"}`}> | |
| text | |
| </div> | |
| </div> | |
| ` | |
| } | |
| } | |
| customElements.define("example-element", ExampleElement) |
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| <!doctype html> | |
| <script type="importmap"> | |
| { | |
| "imports": { | |
| "lit": "https://cdn.jsdelivr.net/gh/lit/dist@3/all/lit-all.min.js", | |
| "lit/directive.js": "https://cdn.jsdelivr.net/gh/lit/dist@3/all/lit-all.min.js" | |
| } | |
| } | |
| </script> | |
| <script type="module" src="./ExampleElement.js"></script> | |
| <example-element></example-element> |
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| import { html, LitElement } from "lit" | |
| import { directive, Directive } from "lit/directive.js" | |
| const makeStyleDirective = (element, Directive) => { | |
| const cssss = new CSSStyleSheet() | |
| return { | |
| directive: directive( | |
| class extends Directive { | |
| host = element | |
| cssss = cssss | |
| } | |
| ), | |
| cssss, | |
| } | |
| } | |
| const map = new Map() | |
| let map_key = 0 | |
| const registry = new FinalizationRegistry((key) => { | |
| const rule = map.get(key) | |
| removeCSSRule(rule) | |
| map.delete(key) | |
| }) | |
| const removeCSSRule = (rule) => { | |
| if (!rule) return | |
| const stylesheet = rule.parentStyleSheet | |
| if (!stylesheet) return | |
| const index = [...stylesheet.cssRules].indexOf(rule) | |
| if (index < 0) return | |
| stylesheet.deleteRule(index) | |
| } | |
| class StyleDirective extends Directive { | |
| host = null | |
| cssss = null | |
| rule = null | |
| key = "" | |
| cache = null | |
| render(template, ...values) { | |
| if (!this.key) { | |
| this.key = "k" + map_key++ | |
| registry.register(this, this.key) | |
| } | |
| const css = `.${this.key} {${String.raw(template, ...values)}}` | |
| if (this.cache !== css) { | |
| removeCSSRule(this.rule) | |
| const rule_index = this.cssss.insertRule(css) | |
| this.rule = this.cssss.cssRules[rule_index] | |
| map.set(this.key, this.rule) | |
| this.cache = css | |
| } | |
| return this.key | |
| } | |
| } | |
| export class StylitElement extends LitElement { | |
| constructor() { | |
| super() | |
| const { directive, cssss } = makeStyleDirective(this, StyleDirective) | |
| this.styleDirective = directive | |
| this._cssss = cssss | |
| } | |
| createRenderRoot() { | |
| const root = super.createRenderRoot() | |
| root.adoptedStyleSheets.push(this._cssss) | |
| return root | |
| } | |
| } |
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