2nd/10_Wiki/Topics/Domain_Programming/Topic_JavaScript/JavaScript_Sets.md

id, title, category, status, verification_status, canonical_id, aliases, duplicate_of, source_trust_level, confidence_score, created_at, updated_at, review_reason, merge_history, tags, raw_sources, applied_in, github_commit

id	title	category	status	verification_status	canonical_id	aliases	duplicate_of	source_trust_level	confidence_score	created_at	updated_at	review_reason	merge_history	tags	raw_sources	applied_in	github_commit
javascript-sets	JavaScript Sets	Frontend	draft	conceptual		Set new Set unique values ES6 Set Set add Set collection		B	0.9	2026-06-23	2026-06-23			javascript js web frontend w3schools set collection es6	https://www.w3schools.com/js/js_sets.asp

JavaScript Sets

🎯 한 줄 통찰 (One-line insight)

A JavaScript Set is a collection of unique values — each value can occur only once — built either from an array or by adding values one at a time, and iterable with for...of. [S1]

🧠 핵심 개념 (Core concepts)

• A Set is a collection of unique values. Each value can only occur once in a Set, and values can be of any type — primitive values or objects. [S1]
• Two ways to create a Set — pass an array to new Set(), or create an empty new Set() and use add(). [S1]
• add() ignores duplicates — adding a value that already exists has no effect; only the first occurrence is retained. [S1]
• Sets are iterable — a for...of loop lists all elements. [S1]
• Type identity — typeof a Set returns "object", and instanceof Set returns true. [S1]
• Set is an ES6 feature with full support in all modern browsers since June 2017. [S1]

🧩 추출된 패턴 (Extracted patterns)

• Deduplicate by construction — feeding values into a Set automatically discards repeats. [S1]
• Empty-then-populate — const s = new Set(); followed by repeated s.add(...). [S1]
• Add variables, not just literals — add() accepts any value, including variables holding objects. [S1]

📖 세부 내용 (Details)

A JavaScript Set is a collection of unique values. Each value can only occur once in a Set. The values can be of any type, primitive values or objects. [S1]

How to create a Set — you can create a JavaScript Set by passing an array to new Set(), or create an empty Set and add values. [S1]

The new Set() Method — pass an array to the new Set() constructor: [S1]

// Create a Set
const letters = new Set(["a","b","c"]);

Create an empty Set and add values with add(): [S1]

// Create a Set
const letters = new Set();

// Add Values to the Set
letters.add("a");
letters.add("b");
letters.add("c");

You can add variables to a Set: [S1]

// Create a Set
const letters = new Set();

// Create Variables
const a = "a";
const b = "b";
const c = "c";

// Add Variables to the Set
letters.add(a);
letters.add(b);
letters.add(c);

The add() Method [S1]

letters.add("d");
letters.add("e");

If you add equal elements, only the first will be saved: [S1]

letters.add("a");
letters.add("b");
letters.add("c");
letters.add("c");
letters.add("c");
letters.add("c");
letters.add("c");
letters.add("c");

Listing the Elements — you can list all the elements of a Set with a for...of loop: [S1]

// Create a Set
const letters = new Set(["a","b","c"]);

// List all Elements
let text = "";
for (const x of letters) {
  text += x;
}

A JavaScript Set is an Object [S1]

typeof letters;      // Returns object

letters instanceof Set;  // Returns true

Browser Support — Set is an ES6 feature (JavaScript 2015), fully supported in all modern browsers since June 2017. [S1]

Browser	Version	Release
Chrome	51	May 2016
Edge	15	Apr 2017
Firefox	54	Jun 2017
Safari	10	Sep 2016
Opera	38	Jun 2016

🛠️ 적용 사례 (Applied in summary)

The page's own snippets are the canonical applied examples — building a letters Set from an array or by adding values, demonstrating that duplicate add() calls collapse to one, and listing elements with for...of. No external project/commit applications found in the source.

💻 코드 패턴 (Code patterns)

Create a Set from an array (language: JavaScript):

const letters = new Set(["a","b","c"]);

Iterate a Set:

let text = "";
for (const x of letters) {
  text += x;
}

⚖️ 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: 0.90
• 중복 검사 결과: 신규 생성 (New discovery)

🔗 지식 그래프 (Knowledge Graph)

• 상위/루트: JavaScript Tutorial
• 관련 개념: JavaScript Set Methods, JavaScript Set Logic, JavaScript Maps
• 참조 맥락: The base concept referenced whenever a collection of unique values is needed.

📚 출처 (Sources)

• [S1] W3Schools — JavaScript Sets — https://www.w3schools.com/js/js_sets.asp

📝 변경 이력 (Change history)

• 2026-06-23: Initial draft synthesized from the W3Schools "JavaScript Sets" page (Astra wiki-curation, P-Reinforce v3.1 format).