[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"verticals":3,"playground-react-weekly-activity-component":44,"search-suggestions":58},[4,20,32],{"id":5,"slug":6,"name":7,"tagline":8,"description":9,"accentFrom":10,"accentTo":11,"icon":12,"defaultLocale":13,"locales":14,"features":16,"position":19},"019fe637-3d33-714b-b57f-23e163ffca0c","dev","Web Development","Read it. Run it. Prove it.","A post a day on modern web development — most with an editable playground and a quiz that explains every answer. Free, no account needed.","violet-500","cyan-400","◇","en",[13,15],"fa",{"courses":17,"paths":17,"articles":17,"exams":18,"flashcards":18,"packages":17,"community":17,"certificates":17,"teams":17,"commerce":17},true,false,0,{"id":21,"slug":22,"name":23,"tagline":24,"description":25,"accentFrom":26,"accentTo":10,"icon":27,"defaultLocale":13,"locales":28,"features":30,"position":31},"019fe637-3dc2-754c-8657-0f175bfee7c6","lang","Languages","Learn a language the way you learn a codebase.","Grammar explained the way good documentation explains an API — one idea at a time, each with a quiz.","amber-400","⌘",[13,15,29],"es",{"courses":18,"paths":18,"articles":17,"exams":18,"flashcards":17,"packages":18,"community":17,"certificates":17,"teams":18,"commerce":18},2,{"id":33,"slug":34,"name":35,"tagline":36,"description":37,"accentFrom":38,"accentTo":39,"icon":40,"defaultLocale":13,"locales":41,"features":42,"position":43},"7b3c16f2-931d-410e-802e-e1fa4edab7de","soft","Soft Skills","The half of the job nobody wrote documentation for.","Weekly, on the parts of working life that decide more than your code does — first weeks, meetings, interviews, promotions, and the people around you. Written from what actually happens, and recorded as a podcast you can listen to on the walk.","emerald-400","teal-300","◉",[13],{"courses":18,"paths":18,"articles":17,"exams":18,"flashcards":18,"packages":18,"community":17,"certificates":18,"teams":18,"commerce":18},3,{"slug":45,"title":46,"summary":47,"html":48,"css":49,"js":50,"config":51,"doc":53},"react-weekly-activity-component","React <Activity> — interactive playground",null,"\u003Cdiv class=\"pg\">\n    \u003Ch1 class=\"pg-title\">🎮 <Activity>: hidden, not gone\u003C\u002Fh1>\n    \u003Cp class=\"pg-sub\">\n      Pick a hide method, then toggle visibility. Watch the counter, the draft, and the\n      two badges — \u003Ccode>renders\u003C\u002Fcode> and \u003Ccode>effect mounts\u003C\u002Fcode> — to see exactly\n      what each method preserves and what it destroys.\n    \u003C\u002Fp>\n\n    \u003Cdiv class=\"banner info show\" id=\"boot\">Loading the real React 19.3.1 runtime from the CDN…\u003C\u002Fdiv>\n\n    \u003Cdiv id=\"app\" hidden>\n      \u003Cdiv class=\"panel\">\n        \u003Cdiv class=\"panel-label\">\u003Cspan class=\"n\">1\u003C\u002Fspan> Hide method\u003C\u002Fdiv>\n        \u003Cdiv class=\"seg\" id=\"modeSeg\" role=\"group\" aria-label=\"Hide method\">\u003C\u002Fdiv>\n        \u003Cdiv class=\"presets\" style=\"margin-top:14px\">\n          \u003Cbutton class=\"btn primary sm\" id=\"toggleBtn\">Hide panel\u003C\u002Fbutton>\n          \u003Cbutton class=\"btn ghost sm\" id=\"bumpBtn\">Bump shared prop\u003C\u002Fbutton>\n          \u003Cbutton class=\"btn ghost sm\" id=\"resetBtn\">Reset demo\u003C\u002Fbutton>\n        \u003C\u002Fdiv>\n      \u003C\u002Fdiv>\n\n      \u003Cdiv class=\"panel\" style=\"margin-top:16px\">\n        \u003Cdiv class=\"panel-label\">\u003Cspan class=\"n\">2\u003C\u002Fspan> The ReportPanel instance\u003C\u002Fdiv>\n        \u003Cdiv id=\"panelMount\">\u003C\u002Fdiv>\n        \u003Cp class=\"hint\" id=\"verdictHint\" style=\"margin-top:12px\">\u003C\u002Fp>\n      \u003C\u002Fdiv>\n\n      \u003Cdiv class=\"panel\" style=\"margin-top:16px\">\n        \u003Cdiv class=\"panel-label\">\u003Cspan class=\"n\">3\u003C\u002Fspan> What React actually did\u003C\u002Fdiv>\n        \u003Cp class=\"hint\" style=\"margin-top:0\">\n          Every line comes from a real \u003Ccode>useEffect\u003C\u002Fcode> mount\u002Fcleanup and render count\n          inside \u003Ccode>ReportPanel\u003C\u002Fcode> — React's own reconciler, observed, not narrated.\n        \u003C\u002Fp>\n        \u003Cdiv class=\"log\" id=\"log\" aria-live=\"polite\">\u003C\u002Fdiv>\n      \u003C\u002Fdiv>\n    \u003C\u002Fdiv>\n  \u003C\u002Fdiv>","\u002F*\n * Shared playground design system — daily-post\n * ============================================\n * Link it from any post's playground\u002Findex.html (no per-post boilerplate):\n *\n *   \u003Clink rel=\"stylesheet\" href=\"..\u002F..\u002F..\u002Fplayground\u002Fassets\u002Fbase.css\" \u002F>\n *\n * The relative path resolves the same locally (posts\u002F\u003Cbase>\u002Fplayground\u002F) and on\n * the deployed host (public\u002Fposts\u002F\u003Cbase>\u002Fplayground\u002F), because build-site.js\n * mirrors this file to public\u002Fplayground\u002Fassets\u002Fbase.css. For a CodeSandbox\n * --embed, playground.js inlines this file so the single-file sandbox still styles.\n *\n * Then write ONLY the demo-specific CSS in your inline \u003Cstyle>. Everything below\n * — tokens, layout, panels, buttons, toggles, sliders, code blocks, status\u002Flog,\n * banners, presets — comes for free and looks consistent across every post.\n *\n * Theme-aware: dark by default, light via prefers-color-scheme AND a\n * [data-theme] override on \u003Chtml> (so a toggle can force either). Accessible:\n * real focus rings, adequate contrast, reduced-motion honored.\n *\u002F\n\n\u002F* ---------- design tokens ---------- *\u002F\n:root {\n  --bg: #0d1117;\n  --bg-grid: #ffffff0a;\n  --panel: #161b22;\n  --panel-2: #0b0e14;\n  --card: #0b0e14;\n  --ink: #e8ebf2;\n  --muted: #9aa4b2;\n  --faint: #6b7688;\n  --line: #232a35;\n  --line-soft: #ffffff12;\n  --accent: #7c9cff;\n  --accent-ink: #0b0e14;\n  --good: #3fb950;\n  --warn: #f0883e;\n  --bad: #f85149;\n  --info: #58a6ff;\n  --radius: 14px;\n  --radius-sm: 9px;\n  --shadow: 0 8px 30px #0006;\n  --shadow-sm: 0 4px 14px #0005;\n  --mono: ui-monospace, SFMono-Regular, \"SF Mono\", Menlo, Consolas, \"Liberation Mono\", monospace;\n  --sans: ui-sans-serif, system-ui, -apple-system, \"Segoe UI\", Roboto, \"Helvetica Neue\", sans-serif;\n  color-scheme: dark;\n}\n\n\u002F* Light theme — system preference, overridable by [data-theme] on \u003Chtml>. *\u002F\n@media (prefers-color-scheme: light) {\n  :root:not([data-theme=\"dark\"]) {\n    --bg: #f4f6fb;\n    --bg-grid: #00000008;\n    --panel: #ffffff;\n    --panel-2: #f0f3f9;\n    --card: #f7f9fc;\n    --ink: #131722;\n    --muted: #5b6472;\n    --faint: #8a93a3;\n    --line: #e2e7f0;\n    --line-soft: #00000010;\n    --accent: #2f6df0;\n    --accent-ink: #ffffff;\n    --good: #1a7f37;\n    --warn: #bc4c00;\n    --bad: #cf222e;\n    --info: #0969da;\n    --shadow: 0 8px 30px #0000001f;\n    --shadow-sm: 0 4px 14px #00000014;\n    color-scheme: light;\n  }\n}\n:root[data-theme=\"light\"] {\n  --bg: #f4f6fb;\n  --bg-grid: #00000008;\n  --panel: #ffffff;\n  --panel-2: #f0f3f9;\n  --card: #f7f9fc;\n  --ink: #131722;\n  --muted: #5b6472;\n  --faint: #8a93a3;\n  --line: #e2e7f0;\n  --line-soft: #00000010;\n  --accent: #2f6df0;\n  --accent-ink: #ffffff;\n  --good: #1a7f37;\n  --warn: #bc4c00;\n  --bad: #cf222e;\n  --info: #0969da;\n  --shadow: 0 8px 30px #0000001f;\n  --shadow-sm: 0 4px 14px #00000014;\n  color-scheme: light;\n}\n\n\u002F* ---------- reset & base ---------- *\u002F\n*, *::before, *::after { box-sizing: border-box; }\n\nbody {\n  margin: 0;\n  min-height: 100vh;\n  font-family: var(--sans);\n  color: var(--ink);\n  background:\n    radial-gradient(circle at 1px 1px, var(--bg-grid) 1px, transparent 0) 0 0 \u002F 24px 24px,\n    var(--bg);\n  display: flex;\n  justify-content: center;\n  align-items: flex-start;\n  padding: clamp(14px, 3vw, 26px);\n  line-height: 1.55;\n  -webkit-font-smoothing: antialiased;\n  text-rendering: optimizeLegibility;\n}\n\n\u002F* The single content column. *\u002F\n.pg {\n  width: 100%;\n  max-width: 860px;\n}\n\n\u002F* ---------- header ---------- *\u002F\n.pg-title {\n  font-size: clamp(1.15rem, 1rem + 1vw, 1.4rem);\n  font-weight: 800;\n  letter-spacing: -0.02em;\n  margin: 0 0 4px;\n  display: flex;\n  align-items: center;\n  gap: 9px;\n}\n.pg-sub {\n  color: var(--muted);\n  font-size: 0.92rem;\n  line-height: 1.5;\n  margin: 0 0 16px;\n  max-width: 66ch;\n}\n.pg-sub strong, .pg-sub b { color: var(--ink); font-weight: 700; }\n.pg-sub code { font-family: var(--mono); background: var(--line-soft); color: var(--accent);\n  padding: 1px 6px; border-radius: 6px; font-size: 0.85em; }\n\n\u002F* ---------- panels ---------- *\u002F\n.panel {\n  background: var(--panel);\n  border: 1px solid var(--line);\n  border-radius: var(--radius);\n  padding: 16px 18px;\n  margin-bottom: 14px;\n  box-shadow: var(--shadow-sm);\n}\n.panel-label {\n  font-size: 0.7rem;\n  text-transform: uppercase;\n  letter-spacing: 0.08em;\n  color: var(--muted);\n  font-weight: 800;\n  margin: 0 0 13px;\n  display: flex;\n  align-items: center;\n  gap: 8px;\n}\n.panel-label .n {\n  display: inline-grid; place-items: center;\n  width: 18px; height: 18px; border-radius: 50%;\n  background: var(--accent); color: var(--accent-ink);\n  font-size: 0.66rem; font-weight: 800;\n}\n\n\u002F* ---------- layout helpers ---------- *\u002F\n.row { display: flex; flex-wrap: wrap; gap: 12px; align-items: center; }\n.row.between { justify-content: space-between; }\n.col { display: flex; flex-direction: column; gap: 10px; }\n.grow { flex: 1 1 0; min-width: 0; }\n.wrap-controls { display: flex; flex-wrap: wrap; gap: 16px 24px; align-items: flex-end; }\n.field { display: flex; flex-direction: column; gap: 7px; min-width: 0; }\n.field > .label, .ctl-label {\n  font-size: 0.7rem; text-transform: uppercase; letter-spacing: 0.04em;\n  color: var(--muted); font-weight: 800;\n}\n\n\u002F* ---------- buttons ---------- *\u002F\n.btn {\n  font: inherit; font-weight: 650; font-size: 0.88rem;\n  cursor: pointer; user-select: none;\n  border: 1px solid var(--line);\n  background: var(--card); color: var(--ink);\n  padding: 9px 15px; border-radius: var(--radius-sm);\n  display: inline-flex; align-items: center; gap: 8px;\n  transition: background .15s ease, border-color .15s ease, transform .05s ease, color .15s ease;\n}\n.btn:hover { background: var(--line-soft); border-color: var(--muted); }\n.btn:active { transform: translateY(1px); }\n.btn:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }\n.btn[disabled] { opacity: 0.45; cursor: not-allowed; }\n.btn.primary { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); }\n.btn.primary:hover { filter: brightness(1.08); background: var(--accent); }\n.btn.good { background: var(--good); border-color: var(--good); color: #04140a; }\n.btn.bad  { background: var(--bad);  border-color: var(--bad);  color: #fff; }\n.btn.ghost { background: transparent; }\n.btn.sm { padding: 6px 11px; font-size: 0.82rem; }\n\n.btn-row { display: flex; flex-wrap: wrap; gap: 9px; }\n\n\u002F* Segmented control — a row of buttons where one is active (aria-pressed). *\u002F\n.seg { display: inline-flex; background: var(--card); border: 1px solid var(--line);\n  border-radius: var(--radius-sm); padding: 3px; gap: 3px; }\n.seg button {\n  font: inherit; font-weight: 650; font-size: 0.84rem; cursor: pointer;\n  border: none; background: transparent; color: var(--muted);\n  padding: 7px 13px; border-radius: 7px;\n  transition: background .15s ease, color .15s ease;\n}\n.seg button:hover { color: var(--ink); }\n.seg button[aria-pressed=\"true\"] { background: var(--accent); color: var(--accent-ink); }\n.seg button:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }\n\n\u002F* Preset chips — worked-example shortcuts. *\u002F\n.presets { display: flex; flex-wrap: wrap; gap: 8px; }\n.presets .btn { background: var(--panel-2); }\n\n\u002F* ---------- toggle switch ---------- *\u002F\n.toggle { display: inline-flex; align-items: center; gap: 10px; cursor: pointer;\n  font-size: 0.88rem; font-weight: 600; user-select: none; }\n.toggle input { position: absolute; opacity: 0; width: 0; height: 0; }\n.switch { position: relative; width: 44px; height: 25px; border-radius: 999px; flex: none;\n  background: var(--line); border: 1px solid var(--line); transition: background .18s ease; }\n.switch::after { content: \"\"; position: absolute; top: 2px; left: 2px; width: 19px; height: 19px;\n  border-radius: 50%; background: #cfd6e4; transition: transform .18s ease; box-shadow: 0 1px 3px #0006; }\n.toggle input:checked + .switch { background: var(--good); border-color: var(--good); }\n.toggle input:checked + .switch::after { transform: translateX(19px); background: #fff; }\n.toggle input:focus-visible + .switch { outline: 2px solid var(--accent); outline-offset: 2px; }\n\n\u002F* ---------- range slider ---------- *\u002F\ninput[type=\"range\"] {\n  -webkit-appearance: none; appearance: none; width: 100%; height: 6px;\n  background: var(--line); border-radius: 999px; outline: none; cursor: pointer; margin: 8px 0;\n}\ninput[type=\"range\"]::-webkit-slider-thumb {\n  -webkit-appearance: none; appearance: none; width: 19px; height: 19px; border-radius: 50%;\n  background: var(--accent); border: 2px solid var(--panel); box-shadow: var(--shadow-sm); cursor: pointer;\n}\ninput[type=\"range\"]::-moz-range-thumb {\n  width: 19px; height: 19px; border-radius: 50%; background: var(--accent);\n  border: 2px solid var(--panel); box-shadow: var(--shadow-sm); cursor: pointer;\n}\ninput[type=\"range\"]:focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; }\n\n\u002F* ---------- text inputs \u002F selects ---------- *\u002F\ninput[type=\"text\"], input[type=\"number\"], input[type=\"search\"], select, textarea {\n  font: inherit; color: var(--ink); background: var(--card);\n  border: 1px solid var(--line); border-radius: var(--radius-sm); padding: 8px 11px; width: 100%;\n}\ntextarea { font-family: var(--mono); font-size: 0.85rem; line-height: 1.6; resize: vertical; }\ninput:focus-visible, select:focus-visible, textarea:focus-visible {\n  outline: 2px solid var(--accent); outline-offset: 1px; border-color: var(--accent);\n}\n\n\u002F* ---------- status \u002F output \u002F log ---------- *\u002F\n.status {\n  display: flex; align-items: center; gap: 9px; flex-wrap: wrap;\n  font-size: 0.9rem; font-weight: 600;\n  padding: 11px 14px; border-radius: var(--radius-sm);\n  background: var(--panel-2); border: 1px solid var(--line); color: var(--ink);\n}\n.status.good { border-color: color-mix(in srgb, var(--good) 55%, var(--line)); }\n.status.warn { border-color: color-mix(in srgb, var(--warn) 55%, var(--line)); }\n.status.bad  { border-color: color-mix(in srgb, var(--bad) 55%, var(--line)); }\n.dot { width: 9px; height: 9px; border-radius: 50%; background: var(--muted); flex: none; }\n.dot.good { background: var(--good); } .dot.warn { background: var(--warn); }\n.dot.bad { background: var(--bad); } .dot.info { background: var(--info); }\n\n.output { background: var(--panel-2); border: 1px solid var(--line); border-radius: var(--radius-sm);\n  padding: 13px 15px; }\n.log { font-family: var(--mono); font-size: 0.8rem; line-height: 1.7; background: var(--card);\n  border: 1px solid var(--line); border-radius: var(--radius-sm); padding: 11px 14px;\n  max-height: 220px; overflow-y: auto; white-space: pre-wrap; }\n\n\u002F* ---------- code block + syntax tokens ---------- *\u002F\n.code {\n  font-family: var(--mono); font-size: 0.82rem; line-height: 1.7;\n  background: var(--panel-2); border: 1px solid var(--line); border-radius: var(--radius-sm);\n  padding: 13px 15px; overflow-x: auto; white-space: pre; tab-size: 2;\n}\n.code .tok-sel  { color: var(--accent); }\n.code .tok-prop { color: #86e29b; }\n.code .tok-kw   { color: #ff9bcb; }\n.code .tok-str  { color: #f0c674; }\n.code .tok-num  { color: #f0883e; }\n.code .tok-cmt  { color: var(--faint); font-style: italic; }\n.code .hl { background: color-mix(in srgb, var(--good) 22%, transparent); border-radius: 4px; padding: 0 3px; }\n\n\u002F* ---------- hint \u002F caption ---------- *\u002F\n.hint { font-size: 0.83rem; color: var(--muted); line-height: 1.55; margin: 10px 0 0; }\n.hint code { font-family: var(--mono); color: var(--ink); background: var(--line-soft);\n  padding: 1px 5px; border-radius: 5px; font-size: 0.86em; }\n.hint strong { color: var(--ink); }\n\n\u002F* ---------- banner (feature-support \u002F notices) ---------- *\u002F\n.banner {\n  display: none; margin-bottom: 14px; padding: 11px 14px; border-radius: 11px;\n  font-size: 0.85rem; line-height: 1.5;\n  color: var(--ink); background: color-mix(in srgb, var(--warn) 12%, var(--panel));\n  border: 1px solid color-mix(in srgb, var(--warn) 45%, var(--line));\n}\n.banner.show { display: block; }\n.banner.info { background: color-mix(in srgb, var(--info) 12%, var(--panel));\n  border-color: color-mix(in srgb, var(--info) 45%, var(--line)); }\n.banner code { font-family: var(--mono); background: var(--line-soft); padding: 1px 5px; border-radius: 5px; }\n\n\u002F* ---------- misc atoms ---------- *\u002F\n.pill { display: inline-flex; align-items: center; gap: 6px; font-size: 0.75rem; font-weight: 700;\n  padding: 3px 9px; border-radius: 999px; background: var(--line-soft); color: var(--muted); }\n.pill.good { color: var(--good); background: color-mix(in srgb, var(--good) 16%, transparent); }\n.pill.bad  { color: var(--bad);  background: color-mix(in srgb, var(--bad) 16%, transparent); }\n.mono { font-family: var(--mono); }\n.muted { color: var(--muted); }\n.big-num { font-family: var(--mono); font-size: 1.6rem; font-weight: 800; letter-spacing: -0.02em; }\n\n\u002F* Optional theme toggle button (top-right). Wire it in JS if you want it. *\u002F\n.theme-btn { position: fixed; top: 12px; right: 12px; z-index: 20; }\n\n\u002F* ---------- responsive ---------- *\u002F\n@media (max-width: 560px) {\n  .panel { padding: 14px; }\n  .wrap-controls { gap: 14px; }\n  .btn { padding: 9px 13px; }\n}\n\n\u002F* ---------- reduced motion ---------- *\u002F\n@media (prefers-reduced-motion: reduce) {\n  *, *::before, *::after { transition-duration: 0.01ms !important; animation-duration: 0.01ms !important; }\n}\n\n\n\u002F* Demo-specific only — base.css owns tokens, panels, buttons, status, log. *\u002F\n  .panelcard {\n    border: 1px solid var(--line); border-radius: var(--radius-sm); padding: 14px;\n    background: var(--panel-2);\n  }\n  .panelcard .head { display: flex; align-items: baseline; justify-content: space-between; gap: 10px; flex-wrap: wrap; }\n  .panelcard h3 { margin: 0; font-size: 1rem; }\n  .badges { display: flex; gap: 6px; flex-wrap: wrap; }\n  .badge { font-size: .72rem; padding: 2px 8px; border-radius: 999px; background: var(--bg); border: 1px solid var(--line); color: var(--muted); font-variant-numeric: tabular-nums; }\n  .counter { font-size: 1.6rem; font-variant-numeric: tabular-nums; margin: 8px 0; }\n  textarea.draft {\n    width: 100%; margin-top: 6px; min-height: 56px; resize: vertical;\n    background: var(--bg); color: inherit; border: 1px solid var(--line);\n    border-radius: var(--radius-sm); padding: 10px; font: inherit;\n  }\n  textarea.draft:focus-visible { outline: 2px solid var(--accent); outline-offset: 1px; }\n  .gone { border: 1px dashed var(--line); border-radius: var(--radius-sm); padding: 20px;\n    text-align: center; color: var(--muted); }","const $ = (id) => document.getElementById(id);\n\nlet React, createRoot;\ntry {\n  \u002F\u002F Pinned to the exact version the article verifies.\n  [React, { createRoot }] = await Promise.all([\n    import(\"https:\u002F\u002Fesm.sh\u002Freact@19.3.1\"),\n    import(\"https:\u002F\u002Fesm.sh\u002Freact-dom@19.3.1\u002Fclient?deps=react@19.3.1\"),\n  ]);\n} catch (err) {\n  $(\"boot\").className = \"banner show\";\n  $(\"boot\").innerHTML =\n    \"\u003Cb>React couldn't load from the CDN\u003C\u002Fb> — you're offline, or a network policy blocked esm.sh. \" +\n    \"This demo deliberately runs the \u003Cem>real\u003C\u002Fem> React reconciler (including the real \" +\n    \"\u003Ccode><Activity>\u003C\u002Fcode> component) rather than imitating it, so there's nothing \" +\n    \"honest to show without it. The article's cheat sheet stands on its own; try again with \" +\n    \"a connection.\";\n  throw err;\n}\n\nconst { createElement: h, useState, useEffect, useRef, Activity } = React;\n\n$(\"boot\").hidden = true;\n$(\"app\").hidden = false;\n\nconst MODES = [\n  { id: \"activity\", label: \"\u003CActivity hidden>\" },\n  { id: \"unmount\", label: \"Unmount ({cond && \u003CX\u002F>})\" },\n  { id: \"css\", label: \"CSS display:none\" },\n];\n\nconst logEl = $(\"log\");\nfunction logLine(text, cls = \"\") {\n  const el = document.createElement(\"div\");\n  el.className = cls;\n  el.textContent = text;\n  logEl.prepend(el);\n  while (logEl.childElementCount > 40) logEl.lastElementChild.remove();\n}\n\nlet nextInstanceId = 1;\n\n\u002F\u002F The exact component from the article: a polling counter (useEffect +\n\u002F\u002F setInterval) and a draft note (useState), plus a \"renders\" badge that\n\u002F\u002F makes the render\u002Feffect split visible instead of just asserted. The ref\n\u002F\u002F increments on every render, hidden or not — reading it during render (not\n\u002F\u002F in an effect) is what lets a hidden-but-still-rendering subtree show up.\nfunction ReportPanel({ revision }) {\n  const [instanceId] = useState(() => nextInstanceId++);\n  const [count, setCount] = useState(0);\n  const [draft, setDraft] = useState(\"\");\n  const renderCount = useRef(0);\n  renderCount.current += 1;\n\n  useEffect(() => {\n    logLine(`▶ instance #${instanceId}: effect mounted (interval started)`, \"good\");\n    const id = setInterval(() => setCount((c) => c + 1), 1000);\n    return () => {\n      clearInterval(id);\n      logLine(`⏹ instance #${instanceId}: effect cleanup (interval cleared)`, \"bad\");\n    };\n  }, [instanceId]);\n\n  return h(\"div\", { className: \"panelcard\" },\n    h(\"div\", { className: \"head\" },\n      h(\"h3\", null, \"Sales report\"),\n      h(\"div\", { className: \"badges\" },\n        h(\"span\", { className: \"badge\" }, `instance #${instanceId}`),\n        h(\"span\", { className: \"badge\" }, `renders: ${renderCount.current}`),\n      )\n    ),\n    h(\"div\", { className: \"counter\" }, \"Records processed: \", h(\"b\", null, count)),\n    h(\"textarea\", {\n      className: \"draft\",\n      value: draft,\n      placeholder: \"Draft note for this report…\",\n      onChange: (e) => setDraft(e.target.value),\n    }),\n    h(\"p\", { className: \"hint\", style: { marginTop: \"8px\" } },\n      `Shared prop (revision): ${revision} — a render caused by this prop proves the subtree is still rendering.`)\n  );\n}\n\nfunction renderControls(mode, setMode) {\n  const wrap = $(\"modeSeg\");\n  wrap.innerHTML = \"\";\n  for (const m of MODES) {\n    const btn = document.createElement(\"button\");\n    btn.textContent = m.label;\n    btn.setAttribute(\"aria-pressed\", String(m.id === mode));\n    btn.addEventListener(\"click\", () => setMode(m.id));\n    wrap.appendChild(btn);\n  }\n}\n\nconst root = createRoot($(\"panelMount\"));\nlet currentHidden = false;\nlet currentRevision = 0;\n\n\u002F\u002F Small stateful wrapper so the plain DOM buttons below can drive React\n\u002F\u002F state without needing their own separate React tree.\nlet setHiddenRef, setRevisionRef, setModeRef;\nfunction AppWrapper() {\n  const [mode, setMode] = useState(\"activity\");\n  const [hidden, setHidden] = useState(false);\n  const [revision, setRevision] = useState(0);\n  setHiddenRef = setHidden;\n  setRevisionRef = setRevision;\n  setModeRef = setMode;\n\n  useEffect(() => {\n    renderControls(mode, setMode);\n    $(\"toggleBtn\").textContent = hidden ? \"Show panel\" : \"Hide panel\";\n    $(\"verdictHint\").textContent = {\n      activity: hidden\n        ? 'Hidden via \u003CActivity mode=\"hidden\">: effect cleanup ran (counter frozen), but state is intact — and a prop bump still causes a render. Watch \"renders\" move while the effect-mount log stays silent.'\n        : \"Visible. Counter is ticking and the draft is editable — this is the same instance every time you hide and show it.\",\n      unmount: hidden\n        ? 'Unmounted: ReportPanel isn\\'t rendered at all right now. \"Bump shared prop\" is a true no-op — there\\'s nothing to render.'\n        : \"Mounted. Hide it and the whole instance (state, effects, everything) will be destroyed, not paused.\",\n      css: hidden\n        ? \"Hidden with plain CSS: the counter is STILL TICKING in the background right now, even though you can't see it — nothing here tore down the effect.\"\n        : \"Visible. Same component, but CSS-hiding it will never stop its effects — only \u003CActivity> and unmounting do that.\",\n    }[mode];\n  }, [mode, hidden]);\n\n  if (mode === \"unmount\") {\n    return hidden\n      ? h(\"div\", { className: \"gone\" }, \"— unmounted: nothing rendered here —\")\n      : h(ReportPanel, { revision });\n  }\n  if (mode === \"css\") {\n    return h(\"div\", { style: { display: hidden ? \"none\" : \"block\" } }, h(ReportPanel, { revision }));\n  }\n  return h(Activity, { mode: hidden ? \"hidden\" : \"visible\" }, h(ReportPanel, { revision }));\n}\n\nroot.render(h(AppWrapper));\n\n$(\"toggleBtn\").addEventListener(\"click\", () => {\n  currentHidden = !currentHidden;\n  setHiddenRef(currentHidden);\n  logLine(`— toggled to ${currentHidden ? \"hidden\" : \"visible\"} —`);\n});\n\n$(\"bumpBtn\").addEventListener(\"click\", () => {\n  currentRevision += 1;\n  setRevisionRef(currentRevision);\n  logLine(`— bumped shared prop to ${currentRevision} —`);\n});\n\n$(\"resetBtn\").addEventListener(\"click\", () => {\n  nextInstanceId = 1;\n  currentHidden = false;\n  currentRevision = 0;\n  logEl.innerHTML = \"\";\n  setModeRef(\"activity\");\n  setHiddenRef(false);\n  setRevisionRef(0);\n});",{"height":52,"autorun":17},520,{"slug":45,"title":54,"excerpt":55,"coverUrl":56,"vertical":57},"React Activity Component: The State Between Render and Remount","React's Activity component hides a subtree without unmounting it — what state, effects, and renders actually do, plus a copy-paste cheat sheet.","\u002Fmedia\u002Fcovers\u002Freact-weekly-activity-component.png",{"slug":6},[59,63,67,71,75,79,83,87,91,95,98,102],{"slug":60,"name":61,"articles":62},"webdev","Webdev",162,{"slug":64,"name":65,"articles":66},"javascript","Javascript",131,{"slug":68,"name":69,"articles":70},"frontend","Frontend",92,{"slug":72,"name":73,"articles":74},"tutorial","Tutorial",64,{"slug":76,"name":77,"articles":78},"css","Css",49,{"slug":80,"name":81,"articles":82},"performance","Performance",27,{"slug":84,"name":85,"articles":86},"typescript","Typescript",23,{"slug":88,"name":89,"articles":90},"react","React",20,{"slug":92,"name":93,"articles":94},"programming","Programming",16,{"slug":96,"name":97,"articles":94},"browser","Browser",{"slug":99,"name":100,"articles":101},"node","Node",14,{"slug":103,"name":104,"articles":105},"html","Html",11]