2026-09-08 16:56:53 +02:00
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// The v8 browser renderer: a runtime-only tagged template.
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2026-09-08 15:59:26 +02:00
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//
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2026-09-08 16:56:53 +02:00
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// Each unique template literal is parsed once, keyed by its (frozen,
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// per-call-site) strings array in a WeakMap: the static parts become a
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// <template> element with markers where the holes are, plus a list of
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// instructions (node paths + hole indices). Every render clones the
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// template and fills the holes. No compile step, no HTML re-parsing on
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// re-render — production speed is a property of the runtime, not of a
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// build tool (this replaces nanohtml's browserify/babel transform).
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//
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// Interpolated values never pass through innerHTML: child values become
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// text nodes or adopted DOM nodes, attribute values go through
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// setAttribute. Only the author-written static strings are parsed as HTML.
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//
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// Known limits (documented, matching or narrowing nanohtml's):
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// - dynamic tag names (html`<${tag}>`) are not supported
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// - holes inside <script>/<style>/<textarea> raw text are not supported
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// - an SVG fragment must include its <svg> root to get the right namespace
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2026-09-08 15:59:26 +02:00
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2026-09-08 16:56:53 +02:00
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const BOOL_PROPS = [
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'async', 'autofocus', 'autoplay', 'checked', 'controls', 'default',
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'defaultchecked', 'defer', 'disabled', 'formnovalidate', 'hidden',
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'ismap', 'loop', 'multiple', 'muted', 'novalidate', 'open', 'playsinline',
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'readonly', 'required', 'reversed', 'selected'
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]
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const templateCache = new WeakMap()
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const TEXT = 0
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const TAG = 1
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const DQ = 2
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const SQ = 3
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const COMMENT = 4
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export default function html (strings, ...values) {
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let entry = templateCache.get(strings)
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if (!entry) {
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entry = parseTemplate(strings)
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templateCache.set(strings, entry)
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}
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return instantiate(entry, values)
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2026-09-08 15:59:26 +02:00
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}
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export { html }
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2026-09-08 16:56:53 +02:00
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// Build the marker HTML for a template literal and parse it once.
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function parseTemplate (strings) {
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let src = ''
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let state = TEXT
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for (let i = 0; i < strings.length; i++) {
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const s = strings[i]
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for (let j = 0; j < s.length; j++) {
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const c = s[j]
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switch (state) {
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case TEXT:
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if (c === '<') {
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if (s.startsWith('!--', j + 1)) {
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state = COMMENT
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j += 3
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} else {
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state = TAG
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}
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}
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break
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case TAG:
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if (c === '>') state = TEXT
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else if (c === '"') state = DQ
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else if (c === "'") state = SQ
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break
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case DQ:
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if (c === '"') state = TAG
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break
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case SQ:
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if (c === "'") state = TAG
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break
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case COMMENT:
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if (c === '-' && s.startsWith('->', j + 1)) {
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state = TEXT
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j += 2
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}
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break
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}
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}
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src += s
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if (i < strings.length - 1) {
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if (state === TEXT) {
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src += `<!--__h${i}__-->`
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} else if (state === DQ || state === SQ) {
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src += `__h${i}__`
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} else if (state === TAG) {
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if (/=\s*$/.test(s)) {
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// unquoted attribute value: attr=${x}
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src += `"__h${i}__"`
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} else {
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// attribute-name position: spread object, <div ${attrs}>
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src += ` __h${i}__ `
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}
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}
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// COMMENT position: holes inside comments are dropped
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}
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}
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const instructions = []
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// <template> parsing drops document-level tags (<body>, <head>, <html>),
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// but choo views legitimately return html`<body>…`. Parse those as a
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// full document instead and use the element itself as the clone root.
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const docRoot = /^\s*<(html|head|body)[\s>]/i.exec(src)
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if (docRoot) {
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const parser = new window.DOMParser()
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const doc = parser.parseFromString(src, 'text/html')
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const tag = docRoot[1].toLowerCase()
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const root = tag === 'html' ? doc.documentElement : tag === 'head' ? doc.head : doc.body
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scanAttrs(root, [], instructions)
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walk(root, [], instructions)
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return { root, instructions }
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}
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const template = document.createElement('template')
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template.innerHTML = src
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walk(template.content, [], instructions)
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return { root: template.content, instructions }
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}
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function walk (node, path, out) {
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const kids = node.childNodes
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for (let i = 0; i < kids.length; i++) {
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const child = kids[i]
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const childPath = path.concat(i)
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if (child.nodeType === 8) { // comment
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const m = /^__h(\d+)__$/.exec(child.data)
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if (m) out.push({ type: 'child', path: childPath, hole: +m[1] })
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} else if (child.nodeType === 1) { // element
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scanAttrs(child, childPath, out)
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walk(child, childPath, out)
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}
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}
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}
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function scanAttrs (el, path, out) {
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for (const attr of [...el.attributes]) {
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const nameMatch = /^__h(\d+)__$/.exec(attr.name)
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if (nameMatch) {
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el.removeAttribute(attr.name)
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out.push({ type: 'spread', path, hole: +nameMatch[1] })
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continue
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}
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if (/__h\d+__/.test(attr.value)) {
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const sole = /^__h(\d+)__$/.exec(attr.value)
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if (sole) {
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// whole value is one hole: apply with type awareness at render
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el.removeAttribute(attr.name)
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out.push({ type: 'attr', path, name: attr.name, hole: +sole[1] })
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} else {
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// static text mixed with holes: string composition
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const parts = attr.value.split(/__h(\d+)__/)
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.map((p, idx) => idx % 2 ? +p : p)
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.filter((p) => p !== '')
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out.push({ type: 'parts', path, name: attr.name, parts })
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}
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}
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}
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}
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function instantiate (entry, values) {
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const frag = entry.root.cloneNode(true)
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// Resolve every target before mutating: child replacements change
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// sibling indices, so paths are only valid against the pristine clone.
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const targets = entry.instructions.map((instr) => resolvePath(frag, instr.path))
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entry.instructions.forEach((instr, i) => {
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const node = targets[i]
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if (instr.type === 'child') {
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node.replaceWith(toNode(values[instr.hole]))
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} else if (instr.type === 'attr') {
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setAttr(node, instr.name, values[instr.hole])
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} else if (instr.type === 'spread') {
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const obj = values[instr.hole]
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if (obj && typeof obj === 'object') {
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for (const key of Object.keys(obj)) setAttr(node, key, obj[key])
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}
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} else if (instr.type === 'parts') {
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const joined = instr.parts
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.map((p) => typeof p === 'number' ? toAttrString(values[p]) : p)
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.join('')
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node.setAttribute(instr.name, joined)
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}
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})
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// A document-level root (<body> etc.) is already an element
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if (frag.nodeType === 1) return frag
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// Single element root unwraps (choo views return one node);
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// anything else stays a fragment.
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let result = null
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for (const child of frag.childNodes) {
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if (child.nodeType === 3 && !child.data.trim()) continue
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if (result === null) {
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result = child
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} else {
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result = frag
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break
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}
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}
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return result === null ? frag : result
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}
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function resolvePath (root, path) {
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let node = root
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for (const index of path) node = node.childNodes[index]
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return node
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}
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function toNode (value) {
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if (value === null || value === undefined) {
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return document.createTextNode('')
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}
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if (value.nodeType) return value
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if (Array.isArray(value)) {
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const frag = document.createDocumentFragment()
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for (const item of value) frag.appendChild(toNode(item))
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return frag
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}
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if (value.__encoded) {
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// raw() output: author-vouched HTML, parsed on purpose
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const t = document.createElement('template')
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t.innerHTML = String(value)
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return t.content
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}
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return document.createTextNode(String(value))
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}
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function setAttr (el, name, value) {
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if (typeof value === 'function') {
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// event handlers are set as properties so nanomorph can copy them
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if (name.startsWith('on')) el[name] = value
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return
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}
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if (BOOL_PROPS.includes(name)) {
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el[name] = !!value
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if (value) el.setAttribute(name, name)
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else el.removeAttribute(name)
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return
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}
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if (value === null || value === undefined || value === false) {
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el.removeAttribute(name)
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return
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}
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if (value === true) {
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el.setAttribute(name, '')
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return
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}
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el.setAttribute(name, String(value))
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if (name === 'value' && 'value' in el) el.value = String(value)
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}
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function toAttrString (value) {
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if (value === null || value === undefined) return ''
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if (typeof value === 'function') return ''
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return String(value)
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}
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