ECMA 6 - Classes

classes.js

"use strict";

class Point
{
  constructor (coordinates) {
    if (!(coordinates instanceof Array)) {
      throw 'Error: Point constructor requires an array of coordinates.';
    }
    this._coordinates = coordinates;
  }
  // Getters
  get coordinates () {
    return this._coordinates;
  }
  get description () {
    var description = '(';
    let separator = ', ';
    for (let coordinate of this.coordinates) {
      description += coordinate + separator;
    }
    if (description.length > 1) {
      description = description.substring(
        0, 
        description.length - separator.length
      );
    }
    return description + ')';
  }
  // Setters
  set coordinates (coordinates) {
    if (!(coordinates instanceof Array)) {
      throw 'Error: Point coordinates must be an array.';
    }
    this._coordinates = coordinates;
  }
  countCoordinates () {
    return this._coordinates.length;
  }
}

class Point2D extends Point
{
  constructor (x, y) {
    super([x, y]);
  }
  // Getters
  get x () {
    return this._coordinates[0];
  }
  get y () {
    return this._coordinates[1];
  }
  // Setters
  set x (x) {
    this._coordinates[0] = x;
  }
  set y (y) {
    this._coordinates[1] = x;
  }
}

var point = new Point2D(4, 6);

console.log(point);                     // Point {_coordinates: Array[2]}
console.log(point.countCoordinates());  // 2
console.log(point.constructor.name);    // Point2D
console.log(point.description);         // (4, 6)