js设计模式之代理模式

应用场景图片懒加载

class MyImage {
    constructor() {
        this.img = new Image()
        document.body.appendChild(this.img)
    }
    setSrc(src) {
        this.img.src = src
    }
}

class ProxyImage {
    constructor() {
        this.proxyImage = new Image()
    }

    setSrc(src) {
        let myImageObj = new MyImage()
        myImageObj.img.src = 'file://xxx.png'  //为本地图片url
        this.proxyImage.src = src
        this.proxyImage.onload = function() {
            myImageObj.img.src = src
        }
    }
}

var proxyImage = new ProxyImage()
proxyImage.setSrc('http://xxx.png') //服务器资源url