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August 23, 2020 23:54
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| <!DOCTYPE html> | |
| <meta charset=utf-8> | |
| <meta name="viewport" content="width=device-width, initial-scale=1"> | |
| <title>Deep Combinator</title> | |
| <style> | |
| [--deep] h1, | |
| [--deep] span { | |
| color: red; | |
| } | |
| </style> | |
| <script type=module> | |
| import jsincss from 'https://unpkg.com/jsincss/index.vanilla.js' | |
| import {selector, process} from 'https://unpkg.com/cssomtools' | |
| import {parseACommaSeparatedListOfComponentValues} from 'https://tomhodgins.github.io/parse-css/index.js' | |
| // Find and support deep selectors | |
| function deepCombinator() { | |
| const lightCSS = [] | |
| // Find all rules with [--deep] | |
| process(selector('[--deep]'), rule => { | |
| // Split by selector lists to find relevant [--deep]-using selectors | |
| const selectors = parseACommaSeparatedListOfComponentValues(rule.selectorText) | |
| .map(selector => selector.map(token => token.toSource()).join('').trim()) | |
| .filter(selector => selector.includes('[--deep]')) | |
| // For each selector in selector list to include [--deep]… | |
| selectors | |
| .map(selector => selector.split(/\s*\[--deep\]\s*/)) | |
| .forEach(([before, after]) => { | |
| const shadows = [...document.querySelectorAll(before || '*')].filter(tag => | |
| tag.shadowRoot | |
| ) | |
| // Find shadowDOM's and apply properties inside | |
| shadows.forEach(shadow => | |
| shadow.shadowRoot.querySelectorAll(after).forEach(child => | |
| [...rule.style].forEach(property => | |
| child.style[property] = rule.style[property] | |
| ) | |
| ) | |
| ) | |
| }) | |
| // Output a copy to light DOM styles without [--deep] | |
| lightCSS.push( | |
| ` | |
| ${ | |
| selectors | |
| .map(selector => selector.replace(/\s*\[--deep\]\s*/, '')) | |
| .join(', ') | |
| } { | |
| ${ | |
| [...rule.style] | |
| .map(property => `${property}: ${rule.style[property]}`) | |
| .join(';') | |
| } | |
| } | |
| ` | |
| ) | |
| }) | |
| return lightCSS.join('') | |
| } | |
| // Run on 'load' and 'reprocessDeepCombinator' events on window | |
| jsincss( | |
| () => deepCombinator(), | |
| window, | |
| ['load', 'reprocessDeepCombinator'] | |
| ) | |
| // Declarative <shadow-dom> support | |
| class ShadowDom extends HTMLElement { | |
| connectedCallback() { | |
| const shadow = this.attachShadow({mode: 'open'}) | |
| shadow.append(...this.childNodes) | |
| } | |
| } | |
| customElements.define('shadow-dom', ShadowDom) | |
| </script> | |
| <div> | |
| <h1>Light DOM</h1> | |
| <span>Light DOM</span> | |
| <shadow-dom> | |
| <h1>ShadowDOM</h1> | |
| <span>ShadowDOM</span> | |
| </shadow-dom> | |
| </div> |
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