【利用AI让知识体系化】7种结构型模式（一）

// 需要适配的类
class RoundPeg {
  constructor(radius) {
    this.radius = radius;
  }
  getRadius() {
    return this.radius;
  }
}
// 目标类
class SquareHole {
  constructor(width) {
    this.width = width;
  }
  getWidth() {
    return this.width;
  }
  fits(peg) {
    return this.getWidth() >= peg.getRadius() * Math.sqrt(2);
  }
}
// 适配器类
class SquarePegAdapter {
  constructor(peg) {
    this.peg = peg;
  }
  getWidth() {
    return this.peg.getRadius() * Math.sqrt(2);
  }
}
// 客户端代码
const roundPeg = new RoundPeg(5);
const squareHole = new SquareHole(10);
if(squareHole.fits(roundPeg)) {
  console.log('The round peg fits into the square hole!');
} else {
  const squarePegAdapter = new SquarePegAdapter(roundPeg);
  if(squareHole.fits(squarePegAdapter)) {
    console.log('The round peg fits into the square hole!');
  } else {
    console.log('The round peg does not fit into the square hole!');
  }
}

// 餐点类
class Meal {
  constructor() {
    this.price = 0;
  }
  getPrice() {
    return this.price;
  }
  setPrice(price) {
    this.price = price;
  }
  getDescription() {
    return '';
  }
}
// 配料装饰器类
class MealDecorator extends Meal {
  constructor(meal) {
    super();
    this.meal = meal;
  }
  getPrice() {
    return this.meal.getPrice() + this.price;
  }
  getDescription() {
    return this.meal.getDescription() + this.description;
  }
}
// 具体的餐点类
class Hamburger extends Meal {
  constructor() {
    super();
    this.setPrice(10);
    this.setDescription('Hamburger');
  }
}
class Pizza extends Meal {
  constructor() {
    super();
    this.setPrice(20);
    this.setDescription('Pizza');
  }
}
// 具体的配料装饰器类
class Cheese extends MealDecorator {
  constructor(meal) {
    super(meal);
    this.setPrice(5);
    this.description = ' + Cheese';
  }
}
class Bacon extends MealDecorator {
  constructor(meal) {
    super(meal);
    this.setPrice(8);
    this.description = ' + Bacon';
  }
}
// 客户端代码
let meal = new Hamburger();
console.log(meal.getDescription() + ' ' + meal.getPrice());
meal = new Cheese(meal);
console.log(meal.getDescription() + ' ' + meal.getPrice());
meal = new Bacon(meal);
console.log(meal.getDescription() + ' ' + meal.getPrice());

// 图片加载类
class ImageLoader {
  constructor(url) {
    this.url = url;
    this.image = null;
  }
  loadImage() {
    if(!this.image) {
      this.image = new Image();
      this.image.src = this.url;
    }
    return this.image;
  }
}
// 图片预加载代理类
class ImagePreloader {
  constructor(url) {
    this.imageLoader = new ImageLoader(url);
  }
  preloadImage() {
    const image = this.imageLoader.loadImage();
    if(!image.complete) {
      image.addEventListener('load', (event) => {
        this.displayImage();
      });
    } else {
      this.displayImage();
    }
  }
  displayImage() {
    console.log('Image is ready to be displayed!');
    // 在这里将图片显示到页面中
  }
}
// 客户端代码
const imagePreloader = new ImagePreloader('http://www.example.com/image.jpg');
imagePreloader.preloadImage();

// DVD播放器电源组件类
class Power {
  constructor() {
    this.isTurnedOn = false;
  }
  turnOn() {
    this.isTurnedOn = true;
    console.log('Power is turned on');
  }
  turnOff() {
    this.isTurnedOn = false;
    console.log('Power is turned off');
  }
}
// DVD播放器显示器组件类
class Display {
  display(title) {
    console.log(`Displaying ${title}`);
  }
}
// DVD播放器音频组件类
class Audio {
  play() {
    console.log('Audio is playing');
  }
  pause() {
    console.log('Audio is paused');
  }
  stop() {
    console.log('Audio is stopped');
  }
}
// DVD播放器外观类
class DVDPlayerFacade {
  constructor() {
    this.power = new Power();
    this.display = new Display();
    this.audio = new Audio();
  }
  play(title) {
    this.power.turnOn();
    this.display.display(title);
    this.audio.play();
  }
  pause() {
    this.audio.pause();
  }
  stop() {
    this.audio.stop();
    this.power.turnOff();
  }
}
// 客户端代码
const dvdPlayer = new DVDPlayerFacade();
dvdPlayer.play('Star Wars: The Last Jedi');
dvdPlayer.pause();
dvdPlayer.stop();