ES5 Inheritance (Working).js

var Point2D = function (x, y) {
  if (x === null || x === undefined) { x = 1; }
  if (y === null || y === undefined) { y = 1; }

  this.x = x;
  this.y = y;
};

Point2D.prototype = {
  equals: function () {
    return this.x === other.x && this.y === other.y;
  }
};

Point = function () {
  Point2D.apply(this, arguments);
};

Point.prototype = new Point2D();

Point.prototype.toString = function () {
  var prefix = [].join.call(arguments, ', ').replace(/,\s$/, '');
  return 'prefix: ' + prefix + ' <' + this.x + ', ' + this.y + '>';
};