🔰inheritance

JS ⟩ value ⟩ object ⟩ class ⟩ inheritance

• access properties on object literal / class's prototype object. (super.prop / super[expr] are valid in any method definition in object literal / class)

• invoke superclass constructor. (super(...args) is valid in class constructors)

// in any method definition
super.prop        // parent's property
super[expr]       // (same)

// ⭐️ subclass
class B extends A { 

    // ⭐️ subclass constructor
    // (if omitted, a default constructor is created automatically)
    constructor(...args) {
        // ⭐️ must call super() before referencing `this`
        super(...args)    // ⭐️ superclass constructor
        // intialize `this` ...
    }
    
    // override method
    method() {
        super.method()        // ⭐️ call parent's method (optional)
        // ...
    }
}

🔴 主題

• derived class init

• override constructor

• override methods

• override class fields

• super - invoke/access superclass/parent's constructor/method/properties.

📗 參考

⭐️ 重點

👥 相關