Encapsulation Principle

Encapsulation is one of the 4 main OOP principles.

It protects the class data from access outside the class body.

Members that are supposed to be accessed only in the class are labeled with _ prefix.

Example of encapsulation

class Car { // Getter and setters that control access // to the private members: get model() { return this._model; } set model(value) { this._model = value; } get manifactureYear() { return this._manifactureYear; } set manifactureYear(value) { this._manifactureYear = value; } } let car = new Car(); car.model = "Toyota Corolla"; car.manifactureYear = 2020; console.log("Year: " + car.manifactureYear); console.log("Model: " + car.model);

Result:

Year: 2020 Model: Toyota Corolla

Explanation:

• The private members (_model and _manifactureYear) are supposed to be accessed / modified by functions defined inside the class (in this case getters and setters).
• Access outside the class body is done the get and set functions (model and manifactureYear).

Example of no encapsulation

class Car {} let car = new Car(); car.model = "Toyota Corolla"; car.manifactureYear = 2020; console.log("Year: " + car.manifactureYear); console.log("Model: " + car.model);

Output:

Year: 2020 Model: Toyota Corolla

All members are accessed outside the class body.