[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"playground-set-methods-union-intersection":3,"verticals":17},{"slug":4,"title":5,"summary":6,"html":7,"css":8,"js":9,"config":10,"doc":13},"set-methods-union-intersection","Set algebra — interactive playground",null,"\u003Cdiv class=\"pg\">\n    \u003Ch1 class=\"pg-title\">🎮 Set algebra, live\u003C\u002Fh1>\n    \u003Cp class=\"pg-sub\">\n      Edit Set A and Set B below and watch \u003Ccode>.union()\u003C\u002Fcode>, \u003Ccode>.intersection()\u003C\u002Fcode>,\n      \u003Ccode>.difference()\u003C\u002Fcode>, and \u003Ccode>.symmetricDifference()\u003C\u002Fcode> update instantly —\n      plus the three boolean checks, \u003Ccode>.isSubsetOf()\u003C\u002Fcode>, \u003Ccode>.isSupersetOf()\u003C\u002Fcode>,\n      and \u003Ccode>.isDisjointFrom()\u003C\u002Fcode>.\n    \u003C\u002Fp>\n\n    \u003Cdiv class=\"banner warn\" id=\"banner\">\n      Your browser doesn't have the native ES2025 Set methods yet, so this demo is computing the\n      same results by hand (the old \u003Ccode>filter\u003C\u002Fcode> + \u003Ccode>has\u003C\u002Fcode> way) just to keep working.\n      The results below are correct either way.\n    \u003C\u002Fdiv>\n\n    \u003Cdiv class=\"panel\">\n      \u003Cdiv class=\"panel-label\">\u003Cspan class=\"n\">1\u003C\u002Fspan> Edit the two sets\u003C\u002Fdiv>\n      \u003Cdiv class=\"setline\">\n        \u003Cdiv class=\"field\">\n          \u003Clabel class=\"label\" for=\"setA\">Set A (comma-separated)\u003C\u002Flabel>\n          \u003Cinput type=\"text\" id=\"setA\" value=\"1, 2, 3\" autocomplete=\"off\" spellcheck=\"false\" \u002F>\n          \u003Cdiv class=\"parsed\" id=\"parsedA\" aria-live=\"polite\">\u003C\u002Fdiv>\n        \u003C\u002Fdiv>\n        \u003Cdiv class=\"field\">\n          \u003Clabel class=\"label\" for=\"setB\">Set B (comma-separated)\u003C\u002Flabel>\n          \u003Cinput type=\"text\" id=\"setB\" value=\"3, 4, 5\" autocomplete=\"off\" spellcheck=\"false\" \u002F>\n          \u003Cdiv class=\"parsed\" id=\"parsedB\" aria-live=\"polite\">\u003C\u002Fdiv>\n        \u003C\u002Fdiv>\n      \u003C\u002Fdiv>\n      \u003Cdiv class=\"btn-row\" style=\"margin-top:14px\">\n        \u003Cbutton class=\"btn ghost\" id=\"reset\">Reset\u003C\u002Fbutton>\n      \u003C\u002Fdiv>\n      \u003Cp class=\"hint\">Type any comma-separated values — numbers or words. Duplicates and blanks are ignored, same as \u003Ccode>new Set(...)\u003C\u002Fcode>.\u003C\u002Fp>\n      \u003Cdiv class=\"presets\" style=\"margin-top:10px\">\n        \u003Cbutton class=\"btn sm\" data-preset=\"numbers\">Preset: numbers (from the intro)\u003C\u002Fbutton>\n        \u003Cbutton class=\"btn sm\" data-preset=\"tags\">Preset: tag diff (before\u002Fafter)\u003C\u002Fbutton>\n      \u003C\u002Fdiv>\n    \u003C\u002Fdiv>\n\n    \u003Cdiv class=\"panel\">\n      \u003Cdiv class=\"panel-label\">\u003Cspan class=\"n\">2\u003C\u002Fspan> The four set-algebra methods\u003C\u002Fdiv>\n      \u003Cpre class=\"code\" id=\"resultCode\">\u003C\u002Fpre>\n      \u003Cdiv class=\"status good\" id=\"status\" style=\"margin-top:12px\">\n        \u003Cspan class=\"dot good\" id=\"dot\">\u003C\u002Fspan>\u003Cspan id=\"statusText\">Ready.\u003C\u002Fspan>\n      \u003C\u002Fdiv>\n      \u003Cp class=\"hint\">\n        \u003Ccode>union\u003C\u002Fcode> merges both, \u003Ccode>intersection\u003C\u002Fcode> keeps only what's shared,\n        \u003Ccode>difference\u003C\u002Fcode> keeps what's in one but not the other, and\n        \u003Ccode>symmetricDifference\u003C\u002Fcode> keeps what's in exactly one. None of these mutate A or B —\n        every line above returns a brand-new \u003Ccode>Set\u003C\u002Fcode>.\n      \u003C\u002Fp>\n    \u003C\u002Fdiv>\n\n    \u003Cdiv class=\"panel\">\n      \u003Cdiv class=\"panel-label\">\u003Cspan class=\"n\">3\u003C\u002Fspan> The three yes\u002Fno checks\u003C\u002Fdiv>\n      \u003Cdiv class=\"predicates\">\n        \u003Cdiv class=\"predicate-row\">\n          \u003Cspan class=\"q\">\u003Ccode>A.isSubsetOf(B)\u003C\u002Fcode> — is every element of A also in B?\u003C\u002Fspan>\n          \u003Cspan class=\"pill\" id=\"pillSubset\">—\u003C\u002Fspan>\n        \u003C\u002Fdiv>\n        \u003Cdiv class=\"predicate-row\">\n          \u003Cspan class=\"q\">\u003Ccode>A.isSupersetOf(B)\u003C\u002Fcode> — does A contain every element of B?\u003C\u002Fspan>\n          \u003Cspan class=\"pill\" id=\"pillSuperset\">—\u003C\u002Fspan>\n        \u003C\u002Fdiv>\n        \u003Cdiv class=\"predicate-row\">\n          \u003Cspan class=\"q\">\u003Ccode>A.isDisjointFrom(B)\u003C\u002Fcode> — do A and B share nothing at all?\u003C\u002Fspan>\n          \u003Cspan class=\"pill\" id=\"pillDisjoint\">—\u003C\u002Fspan>\n        \u003C\u002Fdiv>\n      \u003C\u002Fdiv>\n      \u003Cp class=\"hint\" id=\"predicateHint\">These three always return a plain \u003Ccode>true\u003C\u002Fcode> or \u003Ccode>false\u003C\u002Fcode> — never a new Set.\u003C\u002Fp>\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 CSS ONLY. base.css already provides tokens, layout, panels,\n     buttons, toggles, sliders, code blocks, status\u002Flog, banners, presets. *\u002F\n  .setline { display: flex; flex-wrap: wrap; align-items: center; gap: 10px; }\n  .setline .field { flex: 1 1 220px; }\n  .parsed { display: flex; flex-wrap: wrap; gap: 6px; margin-top: 8px; min-height: 26px; }\n  .chip {\n    font-family: var(--mono); font-size: 0.78rem; font-weight: 700;\n    background: var(--panel-2); border: 1px solid var(--line); color: var(--ink);\n    padding: 3px 9px; border-radius: 999px;\n  }\n  .chip.b { color: var(--accent); border-color: color-mix(in srgb, var(--accent) 45%, var(--line)); }\n  .chip.shared { color: var(--good); border-color: color-mix(in srgb, var(--good) 45%, var(--line)); }\n  .predicates { display: grid; gap: 10px; margin-top: 4px; }\n  .predicate-row {\n    display: flex; align-items: center; justify-content: space-between; gap: 12px;\n    padding: 10px 12px; background: var(--panel-2); border: 1px solid var(--line);\n    border-radius: var(--radius-sm); flex-wrap: wrap;\n  }\n  .predicate-row .q { font-size: 0.86rem; color: var(--ink); }\n  .predicate-row .q code { font-family: var(--mono); background: var(--line-soft); color: var(--accent);\n    padding: 1px 6px; border-radius: 6px; font-size: 0.85em; }","\"use strict\";\n  const $ = (id) => document.getElementById(id);\n\n  \u002F\u002F Feature-detect the ES2025 Set methods (Baseline: Chrome 122, Firefox 127,\n  \u002F\u002F Safari 17.4). If they're missing, fall back to the equivalent manual\n  \u002F\u002F computation so the demo still works — and say so in the banner.\n  const supportsSetMethods =\n    typeof Set.prototype.union === \"function\" &&\n    typeof Set.prototype.intersection === \"function\" &&\n    typeof Set.prototype.difference === \"function\" &&\n    typeof Set.prototype.symmetricDifference === \"function\" &&\n    typeof Set.prototype.isSubsetOf === \"function\" &&\n    typeof Set.prototype.isSupersetOf === \"function\" &&\n    typeof Set.prototype.isDisjointFrom === \"function\";\n\n  if (!supportsSetMethods) $(\"banner\").classList.add(\"show\");\n\n  function unionOf(a, b) {\n    return supportsSetMethods ? a.union(b) : new Set([...a, ...b]);\n  }\n  function intersectionOf(a, b) {\n    return supportsSetMethods ? a.intersection(b) : new Set([...a].filter((x) => b.has(x)));\n  }\n  function differenceOf(a, b) {\n    return supportsSetMethods ? a.difference(b) : new Set([...a].filter((x) => !b.has(x)));\n  }\n  function symmetricDifferenceOf(a, b) {\n    if (supportsSetMethods) return a.symmetricDifference(b);\n    return new Set([...differenceOf(a, b), ...differenceOf(b, a)]);\n  }\n  function isSubsetOf(a, b) {\n    return supportsSetMethods ? a.isSubsetOf(b) : [...a].every((x) => b.has(x));\n  }\n  function isSupersetOf(a, b) {\n    return supportsSetMethods ? a.isSupersetOf(b) : [...b].every((x) => a.has(x));\n  }\n  function isDisjointFrom(a, b) {\n    return supportsSetMethods ? a.isDisjointFrom(b) : [...a].every((x) => !b.has(x));\n  }\n\n  \u002F\u002F Parse a comma-separated field into a Set, converting number-looking\n  \u002F\u002F tokens to actual numbers so `1` and `\"1\"` behave the same as new Set([1,2,3]).\n  function parseSet(str) {\n    const tokens = str\n      .split(\",\")\n      .map((s) => s.trim())\n      .filter((s) => s.length > 0);\n    return new Set(\n      tokens.map((t) => (t !== \"\" && !Number.isNaN(Number(t)) ? Number(t) : t))\n    );\n  }\n\n  function formatVal(v) {\n    return typeof v === \"string\" ? `'${v}'` : String(v);\n  }\n  function formatSet(set) {\n    return `{${[...set].map(formatVal).join(\", \")}}`;\n  }\n  function escapeHtml(s) {\n    return s.replace(\u002F[&\u003C>]\u002Fg, (c) => ({ \"&\": \"&\", \"\u003C\": \"<\", \">\": \">\" }[c]));\n  }\n  function codeLine(a, method, b, resultSet) {\n    return (\n      `\u003Cspan class=\"tok-sel\">${a}\u003C\u002Fspan>.\u003Cspan class=\"tok-prop\">${method}\u003C\u002Fspan>` +\n      `(\u003Cspan class=\"tok-sel\">${b}\u003C\u002Fspan>)` +\n      `  \u003Cspan class=\"tok-cmt\">\u002F\u002F ${escapeHtml(formatSet(resultSet))}\u003C\u002Fspan>`\n    );\n  }\n\n  function renderChips(container, set, otherSet) {\n    container.innerHTML = \"\";\n    if (set.size === 0) {\n      const span = document.createElement(\"span\");\n      span.className = \"hint\";\n      span.textContent = \"(empty)\";\n      container.appendChild(span);\n      return;\n    }\n    for (const v of set) {\n      const chip = document.createElement(\"span\");\n      chip.className = \"chip\" + (otherSet && otherSet.has(v) ? \" shared\" : \"\");\n      chip.textContent = formatVal(v);\n      container.appendChild(chip);\n    }\n  }\n\n  function setPill(el, bool) {\n    el.textContent = bool ? \"true\" : \"false\";\n    el.className = \"pill \" + (bool ? \"good\" : \"bad\");\n  }\n\n  function recompute() {\n    const a = parseSet($(\"setA\").value);\n    const b = parseSet($(\"setB\").value);\n\n    renderChips($(\"parsedA\"), a, b);\n    renderChips($(\"parsedB\"), b, a);\n\n    const union = unionOf(a, b);\n    const intersection = intersectionOf(a, b);\n    const diffAB = differenceOf(a, b);\n    const diffBA = differenceOf(b, a);\n    const symDiff = symmetricDifferenceOf(a, b);\n\n    $(\"resultCode\").innerHTML = [\n      codeLine(\"A\", \"union\", \"B\", union),\n      codeLine(\"A\", \"intersection\", \"B\", intersection),\n      codeLine(\"A\", \"difference\", \"B\", diffAB),\n      codeLine(\"B\", \"difference\", \"A\", diffBA),\n      codeLine(\"A\", \"symmetricDifference\", \"B\", symDiff),\n    ].join(\"\\n\");\n\n    const subset = isSubsetOf(a, b);\n    const superset = isSupersetOf(a, b);\n    const disjoint = isDisjointFrom(a, b);\n    setPill($(\"pillSubset\"), subset);\n    setPill($(\"pillSuperset\"), superset);\n    setPill($(\"pillDisjoint\"), disjoint);\n\n    let statusText;\n    let kind;\n    if (a.size === 0 || b.size === 0) {\n      statusText = \"One of the sets is empty — fill in both to compare them.\";\n      kind = \"warn\";\n    } else if (disjoint) {\n      statusText = \"A and B share nothing — every method that needs overlap comes back empty.\";\n      kind = \"info\";\n    } else if (intersection.size === Math.min(a.size, b.size) && (subset || superset)) {\n      statusText = subset && superset\n        ? \"A and B contain exactly the same elements.\"\n        : subset\n        ? \"A is entirely inside B.\"\n        : \"B is entirely inside A.\";\n      kind = \"good\";\n    } else {\n      statusText = `A and B overlap on ${formatSet(intersection)} and differ elsewhere.`;\n      kind = \"good\";\n    }\n    $(\"statusText\").textContent = statusText;\n    $(\"dot\").className = \"dot \" + kind;\n    $(\"status\").className = \"status \" + kind;\n  }\n\n  const PRESETS = {\n    numbers: { a: \"1, 2, 3\", b: \"3, 4, 5\" },\n    tags: { a: \"react, typescript, css\", b: \"react, vue, css, tailwind\" },\n  };\n\n  document.querySelectorAll(\"[data-preset]\").forEach((btn) => {\n    btn.addEventListener(\"click\", () => {\n      const p = PRESETS[btn.dataset.preset];\n      $(\"setA\").value = p.a;\n      $(\"setB\").value = p.b;\n      recompute();\n    });\n  });\n\n  $(\"setA\").addEventListener(\"input\", recompute);\n  $(\"setB\").addEventListener(\"input\", recompute);\n  $(\"reset\").addEventListener(\"click\", () => {\n    $(\"setA\").value = PRESETS.numbers.a;\n    $(\"setB\").value = PRESETS.numbers.b;\n    recompute();\n  });\n\n  recompute();",{"height":11,"autorun":12},520,true,{"slug":4,"title":14,"excerpt":15,"coverUrl":16},"You've been doing Set math by hand. JavaScript finally shipped `.union()`, `.intersection()`, and friends.","Set has always been missing its obvious operations. ES2025 adds `.union()`, `.intersection()`, `.difference()`, `.symmetricDifference()`, and three boolean predicates — native methods that used to require four lines of spread syntax each.","\u002Fmedia\u002Fcovers\u002Fset-methods-union-intersection.png",[18,33],{"id":19,"slug":20,"name":21,"tagline":22,"description":23,"accentFrom":24,"accentTo":25,"icon":26,"defaultLocale":27,"locales":28,"features":30,"position":32},"019fe637-3d33-714b-b57f-23e163ffca0c","dev","Web Development","Build. Learn. Ship.","Practical courses, engineering-grade articles and open-source tools for people who ship.","violet-500","cyan-400","◇","en",[27,29],"fa",{"courses":12,"paths":12,"articles":12,"exams":31,"flashcards":31,"packages":12,"community":12,"certificates":12,"teams":12,"commerce":12},false,0,{"id":34,"slug":35,"name":36,"tagline":37,"description":38,"accentFrom":39,"accentTo":24,"icon":40,"defaultLocale":27,"locales":41,"features":43,"position":44},"019fe637-3dc2-754c-8657-0f175bfee7c6","lang","Languages","Learn a language the way you learn a codebase.","Structured paths, listening drills and spaced repetition that actually sticks.","amber-400","⌘",[27,29,42],"es",{"courses":12,"paths":12,"articles":31,"exams":31,"flashcards":31,"packages":31,"community":12,"certificates":31,"teams":31,"commerce":12},2]