2nd/10_Wiki/Topic_Programming/Topic_JavaScript/JavaScript_Classes.md

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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-classes	JavaScript Classes	Frontend	draft	conceptual		ES6 classes class syntax constructor method class methods use strict		B	0.89	2026-06-23	2026-06-23			javascript js web frontend w3schools classes oop es6	https://www.w3schools.com/js/js_classes.asp

JavaScript Classes

🎯 한 줄 통찰 (One-line insight)

A JavaScript class, introduced in ES6, is a template for objects (not an object itself), defined with the class keyword and a constructor() method that runs automatically on new. [S1]

🧠 핵심 개념 (Core concepts)

• Classes are ES6 templates — a class is a template for JavaScript objects, defined with the class keyword and a constructor() method. [S1]
• A class is not an object — it is a template from which objects are created. [S1]
• The constructor runs automatically — the constructor method is called automatically when a new object is created with new. [S1]
• Constructor rules — it must use the exact name constructor, executes automatically, and initializes properties. [S1]
• Class methods are defined inside the class body and can take parameters. [S1]
• Strict mode — classes require "strict mode" compliance (e.g. variables must be declared with const/let). [S1]

🧩 추출된 패턴 (Extracted patterns)

• constructor + this initialization — assign incoming arguments to this.* in the constructor to set up object state. [S1]
• Method computes from state — methods like age() derive values from the instance's own properties (e.g. this.year). [S1]
• Pass external data as a parameter — when a method needs outside data (like the current year), pass it in as an argument rather than recomputing. [S1]

📖 세부 내용 (Details)

JavaScript Class Syntax ES6 introduced JavaScript Classes as templates for objects. The basic syntax uses the class keyword with a constructor() method: [S1]

class ClassName {
  constructor() { ... }
}

A concrete example: [S1]

class Car {
  constructor(name, year) {
    this.name = name;
    this.year = year;
  }
}

A JavaScript class is not an object. It is a template for JavaScript objects. [S1]

Using a Class Instantiate with new: [S1]

const myCar1 = new Car("Ford", 2014);
const myCar2 = new Car("Audi", 2019);

The constructor method is called automatically when a new object is created. [S1]

The Constructor Method The constructor must use the exact name constructor, executes automatically when objects are created, and initializes properties. [S1]

Class Methods A method computing the car's age from this.year: [S1]

class Car {
  constructor(name, year) {
    this.name = name;
    this.year = year;
  }
  age() {
    const date = new Date();
    return date.getFullYear() - this.year;
  }
}

const myCar = new Car("Ford", 2014);
document.getElementById("demo").innerHTML =
"My car is " + myCar.age() + " years old.";

A method that accepts a parameter: [S1]

class Car {
  constructor(name, year) {
    this.name = name;
    this.year = year;
  }
  age(x) {
    return x - this.year;
  }
}

const date = new Date();
let year = date.getFullYear();

const myCar = new Car("Ford", 2014);
document.getElementById("demo").innerHTML=
"My car is " + myCar.age(year) + " years old.";

"use strict" Classes require "strict mode" compliance — variables must be properly declared: [S1]

class Car {
  constructor(name, year) {
    this.name = name;
    this.year = year;
  }
  age() {
    // date = new Date();  // This will not work
    const date = new Date(); // This will work
    return date.getFullYear() - this.year;
  }
}

🛠️ 적용 사례 (Applied in summary)

The Car class is the running applied example — defining name/year in the constructor, deriving age in a method (with and without a parameter), and demonstrating strict-mode variable declaration. No external project/commit applications found in the source.

💻 코드 패턴 (Code patterns)

Define a class and instantiate it (language: JavaScript):

class Car {
  constructor(name, year) {
    this.name = name;
    this.year = year;
  }
}
const myCar1 = new Car("Ford", 2014);

Add a method that uses instance state:

age() {
  const date = new Date();
  return date.getFullYear() - this.year;
}

⚖️ 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: 0.89
• 중복 검사 결과: 신규 생성 (New discovery)

🔗 지식 그래프 (Knowledge Graph)

• 상위/루트: JavaScript Tutorial
• 관련 개념: JavaScript Class Inheritance, JavaScript Class Static, JavaScript Objects, JavaScript Object Constructors
• 참조 맥락: The foundation for object-oriented JavaScript; extended by class inheritance and static-method pages.

📚 출처 (Sources)

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

📝 변경 이력 (Change history)

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