[Javascript] ES6 class

ES6 class

// Person : parent class
// extends : inheritance between classes, automatically sets prototype
class Student extends Person {
  university = "KNU"; // public field
  _studyHours = 0; // private filed
  _course;
  static numSubjects = 10; // static public field

  // constructor method, called by new operator
  constructor(fullName, birthYear, startYear, course) {
    super(fullName, birthYear); // call to parent class

    this.startYear = startYear; // instance property
    this._course = course; // redefining private field
  }

  // public method
  introduce() {
    console.log(`hi I am ${this.fullName}`);
  }

  study(h) {
    // Referencing private field and method
    this._makeCoffe();
    this._studyHours += h;
  }

  _makeCoffe() {
    return "coffee for you";
  }

  // getter and setter method
  get testScore() {
    return this._testScore;
  }

  // use _ to set property with same name as method
  set testScore(score) {
    this._testScore = score <= 20 ? score : 0;
  }

  // static method (cannot access instance properties nor method)
  static printCurriculum() {
    console.log(`There are ${this.numSubjects} subjects`);
  }
}

• extends 키워드를 이용하여 상속
• private 변수, 메서드는 보통 under bar _ 를 쓰는데, 이것은 그냥 convention임
• static 키워드를 이용하여 인스턴스가 아니라 class 자체에서 호출가능

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ref :
Class basic syntax