//Subject
class Graphic {
    constructor(fileName) {
        this._fileName = fileName;
    }

    getFileName() {
        return this._fileName;
    }
}

//RealSubject
class CImage extends Graphic { 
    constructor(fileName) {
        super(fileName);
    }

    //Request()
    draw() {
        console.log("draw " + this._fileName);
    }
}

//Proxy
class ImageProxy extends Graphic { 
    constructor(fileName) {
        super(fileName);
    }

    getImage() {
        if (this._image == undefined) {
            this._image = new CImage(this._fileName);
        }
        return this._image;
    }

    draw() {
        this.getImage().draw();
    }
}

//Client
let proxy = new ImageProxy("1.png");
//operation without creating a RealSubject
let fileName = proxy.getFileName();
//forwarded to the RealSubject
proxy.draw();

console.log("fileName is", fileName);