Decorator 實作範例 1

decorator1.js

function Sale(price) {
  this.price = price || 100;
}
Sale.prototype.getPrice = function() {
  return this.price;
};
Sale.prototype.decorate = function (decorator) {
  var F = function(){},
      overrides = this.constructor.decorators[decorator],
      i, newobj;
  F.prototype = this;
  newobj = new F();
  newobj.uber = F.prototype;
  for(i in overrides) {
    if (overrides.hasOwnProperty(i)) {
      newobj[i] = overrides[i];
    }
  }
  return newobj;
};

Sale.decorators = {};
Sale.decorators.fedtax = {
  getPrice: function() {
    var price = this.uber.getPrice();
    price += price * 0.05;
    return price;
  }
};

Sale.decorators.quebec = {
  getPrice: function() {
    var price = this.uber.getPrice();
    price += price * 0.075;
    return price;
  }
};

Sale.decorators.money = {
  getPrice: function() {
    return '$' + this.uber.getPrice().toFixed(2);
  }
};

Sale.decorators.cdn = {
  getPrice: function() {
    return 'CDN$' + this.uber.getPrice().toFixed(2);
  }
};

var sale = new Sale(100);
sale = sale.decorate('fedtax');
sale = sale.decorate('quebec');
sale = sale.decorate('money');
console.log(sale.getPrice());