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: html-drag-and-drop
+title: "HTML Drag and Drop"
+category: "Frontend"
+status: "draft"
+verification_status: "conceptual"
+canonical_id: ""
+aliases: ["Drag and Drop API", "draggable attribute", "dataTransfer", "ondragstart", "ondrop", "HTML5 drag and drop"]
+duplicate_of: ""
+source_trust_level: "B"
+confidence_score: 0.89
+created_at: 2026-06-23
+updated_at: 2026-06-23
+review_reason: ""
+merge_history: []
+tags: ["html", "web", "frontend", "w3schools", "drag-and-drop", "api", "html5"]
+raw_sources: ["https://www.w3schools.com/html/html5_draganddrop.asp"]
+applied_in: []
+github_commit: ""
+---
+
+# [[HTML Drag and Drop]]
+
+## 🎯 한 줄 통찰 (One-line insight)
+The HTML Drag and Drop API lets an element be dragged and dropped by marking it `draggable="true"` and wiring `ondragstart`, `ondragover`, and `ondrop` handlers that pass data through the `dataTransfer` object. [S1]
+
+## 🧠 핵심 개념 (Core concepts)
+- **Drag and Drop API** — enables an element to be dragged and dropped, a common interaction where users grab an object and move it elsewhere. [S1]
+- **`draggable="true"`** — the attribute that makes an element draggable. [S1]
+- **`dataTransfer`** — the object that carries data between the drag source and drop target via `setData()` / `getData()`. [S1]
+- **Default targets reject drops** — elements cannot receive drops by default; you must call `preventDefault()` in the dragover handler to allow a drop. [S1]
+
+## 🧩 추출된 패턴 (Extracted patterns)
+- **`ondragstart` + `setData()`** — when dragging starts, store the data type and the dragged element's value. [S1]
+- **`ondragover` + `preventDefault()`** — allow dropping by preventing the default behavior that blocks it. [S1]
+- **`ondrop` + `getData()` + `appendChild()`** — on drop, retrieve the data using the same type used in `setData()`, then move the element into the drop target. [S1]
+
+## 📖 세부 내용 (Details)
+**What it is**
+The HTML Drag and Drop API enables an element to be dragged and dropped. Browser support begins with Chrome 4.0, Internet Explorer 9.0, Firefox 3.5, Safari 6.0, and Opera 12.0. [S1]
+
+**Make an element draggable**
+Set the `draggable` attribute to `true`: [S1]
+```html
+<img id="img1" draggable="true">
+```
+or
+```html
+<p id="p1" draggable="true">Draggable text</p>
+```
+
+**Complete example**
+```html
+<!DOCTYPE HTML>
+<html>
+<head>
+<script>
+function dragstartHandler(ev) {
+  ev.dataTransfer.setData("text", ev.target.id);
+}
+
+function dragoverHandler(ev) {
+  ev.preventDefault();
+}
+
+function dropHandler(ev) {
+  ev.preventDefault();
+  const data = ev.dataTransfer.getData("text");
+  ev.target.appendChild(document.getElementById(data));
+}
+</script>
+</head>
+<body>
+
+<div id="div1" ondrop="dropHandler(event)" ondragover="dragoverHandler(event)"></div>
+
+<img id="img1" src="img_logo.gif" draggable="true" ondragstart="dragstartHandler(event)" width="336" height="69">
+
+</body>
+</html>
+```
+
+**The events explained**
+- **`ondragstart` and `setData()`** — the `dataTransfer.setData()` method sets the data type and the value of the dragged data. [S1]
+- **`ondragover`** — by default, elements cannot receive drops. To allow a drop, call `preventDefault()` in the dragover handler. [S1]
+- **`ondrop`** — when the dragged data is dropped, retrieve it via `dataTransfer.getData()` using the same type that was specified in `setData()`. The example then appends the dragged element into the drop target. [S1]
+
+## 🛠️ 적용 사례 (Applied in summary)
+The complete example above is the canonical applied case: dragging an `<img>` into a `<div>` drop zone. No external project/commit applications found in the source.
+
+## 💻 코드 패턴 (Code patterns)
+Drag start — store the id (JavaScript):
+```javascript
+function dragstartHandler(ev) {
+  ev.dataTransfer.setData("text", ev.target.id);
+}
+```
+Allow drop (JavaScript):
+```javascript
+function dragoverHandler(ev) {
+  ev.preventDefault();
+}
+```
+Perform drop — move the element (JavaScript):
+```javascript
+function dropHandler(ev) {
+  ev.preventDefault();
+  const data = ev.dataTransfer.getData("text");
+  ev.target.appendChild(document.getElementById(data));
+}
+```
+
+## ⚖️ 모순 및 업데이트 (Contradictions & updates)
+No contradictions found in the source. Note the non-obvious requirement: a drop target rejects drops unless `preventDefault()` is called in its dragover handler. [S1]
+
+## ✅ 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:** 0.89
+- **중복 검사 결과:** 신규 생성 (New discovery)
+
+## 🔗 지식 그래프 (Knowledge Graph)
+- **상위/루트:** [[HTML Tutorial]]
+- **관련 개념:** [[HTML Web APIs]], [[HTML Geolocation]], [[HTML Web Storage]], [[HTML Web Workers]]
+- **참조 맥락:** Referenced whenever building interactive UIs where users rearrange or move elements directly.
+
+## 📚 출처 (Sources)
+- [S1] W3Schools — HTML Drag and Drop — https://www.w3schools.com/html/html5_draganddrop.asp
+
+## 📝 변경 이력 (Change history)
+- 2026-06-23: Initial draft synthesized from the W3Schools "HTML Drag and Drop" page (Astra wiki-curation, P-Reinforce v3.1 format).