docs(10_Wiki): W3Schools 위키화 — HTML/CSS/JavaScript(core)

W3Schools 튜토리얼을 P-Reinforce v3.1 포맷으로 위키화(영어 본문, 한/영 섹션 헤더). - Topic_HTML: 59문서 (튜토리얼+예제, 레퍼런스/메타 제외) - Topic_CSS: 190문서 (메인 + Advanced/Flexbox/Grid/RWD 전체) - Topic_JavaScript: 120문서 (코어 언어; Temporal/DOM상세/BOM/WebAPI/AJAX/jQuery/Graphics 등은 후속) 각 폴더 00_INDEX.md(MOC) 포함. 코드 verbatim, 미확인분은 "Not found in source" 표기. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-06-23 19:21:18 +09:00
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+---
+id: css-advanced-dropdowns
+title: "CSS Advanced Dropdowns"
+category: "Frontend"
+status: "draft"
+verification_status: "conceptual"
+canonical_id: ""
+aliases: ["advanced dropdown", "right-aligned dropdown", "dropdown image", "dropdown navbar", "navbar dropdown"]
+duplicate_of: ""
+source_trust_level: "B"
+confidence_score: 0.88
+created_at: 2026-06-23
+updated_at: 2026-06-23
+review_reason: ""
+merge_history: []
+tags: ["css", "web", "frontend", "w3schools", "dropdown", "navbar", "alignment"]
+raw_sources: ["https://www.w3schools.com/css/css_dropdowns_advanced.asp"]
+applied_in: []
+github_commit: ""
+---
+
+# [[CSS Advanced Dropdowns]]
+
+## 🎯 한 줄 통찰 (One-line insight)
+Building on the basic hover dropdown, advanced dropdowns control alignment with `right: 0;` / `left: 0;`, embed images in the content box, and drop the menu into a floated navbar `<li class="dropdown">`. [S1]
+
+## 🧠 핵심 개념 (Core concepts)
+- **Alignment control** — whether the dropdown content opens left-to-right or right-to-left is determined by the `left` and `right` properties on `.dropdown-content`; adding `right: 0;` makes it go from right to left. [S1]
+- **Inline-block wrapper** — for aligned and navbar dropdowns the wrapper uses `display: inline-block` (and `position: relative`) so it sits in the flow next to siblings. [S1]
+- **Stacking** — advanced dropdowns add `z-index: 1;` to the content box so it layers above following content. [S1]
+- **Dropdown with image** — a dropdown can reveal an image plus a `.desc` caption instead of plain text/links, triggered by hovering an image trigger. [S1]
+- **Dropdown navbar** — a dropdown can live inside a navigation bar as one `<li class="dropdown">` among other `<li>` links, with its menu absolutely positioned beneath the bar. [S1]
+
+## 🧩 추출된 패턴 (Extracted patterns)
+- **Side anchoring** — set `right: 0;` (or `left: 0;`) on the absolutely positioned content box to anchor the menu to either edge of its wrapper. [S1]
+- **Image-as-trigger** — use an `<img>` as the hover trigger and reveal a larger image + caption in the content box. [S1]
+- **Navbar integration** — float `<li>` items and treat one as `li.dropdown { display: inline-block; }`, sharing hover styling with the bar links via grouped selectors. [S1]
+
+## 📖 세부 내용 (Details)
+**Overview**
+This page covers three advanced dropdown techniques: a right-aligned dropdown, a dropdown containing an image, and a dropdown inside a navbar. To control direction, the page notes: if you want the dropdown menu to go from right to left instead of left to right, add `right: 0;`. [S1]
+
+**Example 1 — Right-aligned (Aligned Dropdown Content)**
+Two dropdowns are floated left and right; the left one forces `left:0;` on its content while the right one uses the stylesheet default with `right: 0;`. The wrapper is `display: inline-block;` and the content box has `z-index: 1;`: [S1]
+```html
+<!DOCTYPE html>
+<html>
+<head>
+<style>
+.dropbtn {
+  background-color: #4CAF50;
+  color: white;
+  padding: 16px;
+  font-size: 16px;
+  border: none;
+  cursor: pointer;
+}
+
+.dropdown {
+  position: relative;
+  display: inline-block;
+}
+
+.dropdown-content {
+  display: none;
+  position: absolute;
+  right: 0;
+  background-color: #f9f9f9;
+  min-width: 160px;
+  box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
+  z-index: 1;
+}
+
+.dropdown-content a {
+  color: black;
+  padding: 12px 16px;
+  text-decoration: none;
+  display: block;
+}
+
+.dropdown-content a:hover {background-color: #f1f1f1;}
+
+.dropdown:hover .dropdown-content {
+  display: block;
+}
+
+.dropdown:hover .dropbtn {
+  background-color: #3e8e41;
+}
+</style>
+</head>
+<body>
+
+<h2>Aligned Dropdown Content</h2>
+<p>Determine whether the dropdown content should go from left to right or right to left with the left and right properties.</p>
+
+<div class="dropdown" style="float:left;">
+  <button class="dropbtn">Left</button>
+  <div class="dropdown-content" style="left:0;">
+    <a href="#">Link 1</a>
+    <a href="#">Link 2</a>
+    <a href="#">Link 3</a>
+  </div>
+</div>
+
+<div class="dropdown" style="float:right;">
+  <button class="dropbtn">Right</button>
+  <div class="dropdown-content">
+    <a href="#">Link 1</a>
+    <a href="#">Link 2</a>
+    <a href="#">Link 3</a>
+  </div>
+</div>
+
+</body>
+</html>
+```
+
+**Example 2 — Dropdown with Image**
+Hovering a small image reveals a larger image and a `.desc` caption inside the dropdown content: [S1]
+```html
+<!DOCTYPE html>
+<html>
+<head>
+<style>
+.dropdown {
+  position: relative;
+}
+
+.dropdown-content {
+  display: none;
+  position: absolute;
+  background-color: #f9f9f9;
+  min-width: 160px;
+}
+
+.dropdown:hover .dropdown-content {
+  display: block;
+}
+
+.desc {
+  padding: 15px;
+  text-align: center;
+}
+</style>
+</head>
+<body>
+
+<h2>Dropdown Image</h2>
+<p>Move the mouse over the image below to open the dropdown content.</p>
+
+<div class="dropdown">
+  <img src="img_5terre.jpg" alt="Cinque Terre" width="100" height="50">
+  <div class="dropdown-content">
+    <img src="img_5terre.jpg" alt="Cinque Terre" width="300" height="200">
+    <div class="desc">Beautiful Cinque Terre</div>
+  </div>
+</div>
+
+</body>
+</html>
+```
+
+**Example 3 — Dropdown Navbar**
+A navigation bar (`ul` with `overflow: hidden` and a dark background) where one `<li class="dropdown">` contains a `.dropbtn` link and an absolutely positioned `.dropdown-content`. Bar links and the dropdown button share hover styling via grouped selectors: [S1]
+```html
+<!DOCTYPE html>
+<html>
+<head>
+<style>
+body {
+  margin: 0;
+  padding: 0;
+}
+h2, p {
+  margin: 10px;
+}
+ul {
+  list-style-type: none;
+  margin: 0;
+  padding: 0;
+  overflow: hidden;
+  background-color: #38444d;
+}
+li {
+  float: left;
+}
+li a, .dropbtn {
+  display: inline-block;
+  color: white;
+  text-align: center;
+  padding: 14px 16px;
+  text-decoration: none;
+}
+li a:hover, .dropdown:hover .dropbtn {
+  background-color: red;
+}
+li.dropdown {
+  display: inline-block;
+}
+.dropdown-content {
+  display: none;
+  position: absolute;
+  background-color: #f9f9f9;
+  min-width: 160px;
+  box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
+  z-index: 1;
+}
+.dropdown-content a {
+  color: black;
+  padding: 12px 16px;
+  text-decoration: none;
+  display: block;
+  text-align: left;
+}
+.dropdown-content a:hover {background-color: #f1f1f1;}
+.dropdown:hover .dropdown-content {
+  display: block;
+}
+</style>
+</head>
+<body>
+<ul>
+<li><a href="#home">Home</a></li>
+<li><a href="#news">News</a></li>
+<li class="dropdown">
+<a href="javascript:void(0)" class="dropbtn">Dropdown</a>
+<div class="dropdown-content">
+<a href="#">Link 1</a>
+<a href="#">Link 2</a>
+<a href="#">Link 3</a>
+</div>
+</li>
+</ul>
+<h2>Dropdown Menu in Navbar</h2>
+<p>Hover over the "Dropdown" link to see the dropdown menu.</p>
+</body>
+</html>
+```
+
+## 🛠️ 적용 사례 (Applied in summary)
+The page's three complete examples — right/left aligned dropdowns, an image dropdown, and a navbar dropdown — are the applied demonstrations. No external project/commit applications found in the source.
+
+## 💻 코드 패턴 (Code patterns)
+Edge alignment of the content box (language: CSS):
+```css
+.dropdown-content {
+  position: absolute;
+  right: 0; /* anchor to right edge; use left: 0; for left edge */
+  z-index: 1;
+}
+```
+Navbar dropdown item (language: CSS):
+```css
+li.dropdown {
+  display: inline-block;
+}
+.dropdown:hover .dropdown-content {
+  display: block;
+}
+```
+
+## ⚖️ 모순 및 업데이트 (Contradictions & updates)
+No contradictions found in the source.
+
+## ✅ 검증 상태 및 신뢰도
+- **상태:** draft
+- **검증 단계:** conceptual (실제 적용 사례 발견 시 applied/validated로 승격 가능)
+- **출처 신뢰도:** B (W3Schools — widely used educational reference, not a primary standards body)
+- **신뢰 점수:** 0.88
+- **중복 검사 결과:** 신규 생성 (New discovery)
+
+## 🔗 지식 그래프 (Knowledge Graph)
+- **상위/루트:** [[CSS Tutorial]]
+- **관련 개념:** [[CSS Dropdowns]], [[CSS Navigation Bar]], [[CSS Position]]
+- **참조 맥락:** Referenced when a basic dropdown needs edge alignment, image content, or integration into a site navigation bar.
+
+## 📚 출처 (Sources)
+- [S1] W3Schools — CSS Advanced Dropdowns — https://www.w3schools.com/css/css_dropdowns_advanced.asp
+
+## 📝 변경 이력 (Change history)
+- 2026-06-23: Initial draft synthesized from the W3Schools "CSS Advanced Dropdowns" page (Astra wiki-curation, P-Reinforce v3.1 format).