Constructor Initialization

Initialize instance fields in a constructor.

constructor_init.js

const width = 4;
class Box {
  constructor(width, height) {
    this.area = width * height;
  }

  getArea() {
    return this.area;
  }
}

const area = new Box(width, 3).getArea();

console.log("width=" + width);
console.log("area=" + area);

constructor-init The constructor runs when an instance is created. Use it to compute and store the fields that later methods need.