淘宝放大镜效果，附源码！

描述：

javaScript面向对象——淘宝放大镜实现图片的引用是一个大图，一个小图。传输用的ajax，记得改成自己的ip地址，js和html都改一下。

最终效果如下:

实现过程：

js文件：LoadMethod.js

class LoadMethod{
    static get LOAD_IMG_FINISH(){
        return "load_img_finish";
    }
    static init(sourceList){
        let img=new Image();
        img.num=0;
        img.sourceList=sourceList;
        img.targetList={};
        img.addEventListener("load",LoadMethod.loadHandler);
        img.src=sourceList[0];

    }
    static loadHandler(e){
        let images=this.cloneNode(false);
        let name=this.sourceList[this.num];
        name=name.slice(name.lastIndexOf("/")+1,name.lastIndexOf("."));
        this.targetList[name]={src:images.src,elem:images,width:images.width,height:images.height};
        this.num++;
        if(this.num>this.sourceList.length-1){
            this.removeEventListener("load",LoadMethod.loadHandler);
            let evt=new Event(LoadMethod.LOAD_IMG_FINISH);
            evt.targetList=this.targetList;
            document.dispatchEvent(evt);
            return;
        }
        this.src=this.sourceList[this.num];

    }
}
class Drag{
    static dragElem(elem,rect,parent){
        Drag.drageHandler=Drag.mouseHandler.bind(elem);
        elem.rect=rect;
        elem.parent=parent;
        elem.addEventListener("mousedown",Drag.drageHandler);
    }
    static removeDrag(elem){
        elem.removeEventListener("mousedown",Drag.drageHandler);
        Drag.drageHandler=null;
    }
    static mouseHandler(e){
        if(e.type==="mousedown"){
            this.addEventListener("mouseup",Drag.drageHandler);
            this.offsetPoint={x:e.offsetX,y:e.offsetY};
            document.addEventListener("mousemove",Drag.drageHandler);
        }else if(e.type==="mousemove"){
           if(!this.rect){
               this.rect=this.parent.getBoundingClientRect();
           }
            let obj={
                left:e.x-this.offsetPoint.x-this.rect.left+"px",
                top:e.y-this.offsetPoint.y-this.rect.top+"px",
                position:"absolute"
            };
            Object.assign(this.style,obj);
            let elemRect=this.getBoundingClientRect();
            if(elemRect.left<this.rect.left){
                this.style.left="0px";
            }
            if(elemRect.right>this.rect.right){
                this.style.left=this.rect.right-elemRect.width-this.rect.left+"px";
            }
            if(elemRect.top<this.rect.top){
                this.style.top="0px";
            }
            if(elemRect.bottom>this.rect.bottom){
                this.style.top=this.rect.bottom-elemRect.height-this.rect.top+"px";
            }
            let evt=new Event(Drag.ELEM_MOVE_EVENT);
            evt.point={x:this.offsetLeft,y:this.offsetTop};
            this.dispatchEvent(evt);
        }else if(e.type==="mouseup"){
            this.removeEventListener("mouseup",Drag.drageHandler);
            document.removeEventListener("mousemove",Drag.drageHandler);
        }
    }
    static get ELEM_MOVE_EVENT(){
        return "elem_move_event";
    }
}

ZoomClasses.js

class ZoomClasses{
    constructor(panrent){
        this.bindHandler=this.loadFinishHandler.bind(this);
        document.addEventListener(LoadMethod.LOAD_IMG_FINISH,this.bindHandler);
        this.zoomView=this.createView();
        panrent.appendChild(this.zoomView);
    }
    createView(){
        if(this.zoomView) return this.zoomView;
        let div=document.createElement("div");
        this.minDiv=document.createElement("div");
        this.maxDiv=document.createElement("div");
        this.dragDiv=document.createElement("div");
        Object.assign(div.style,{
            position:"relative",
        });
        this.minDiv.appendChild(this.dragDiv);
        div.appendChild(this.minDiv);
        div.appendChild(this.maxDiv);
        this.dragDiv.addEventListener(Drag.ELEM_MOVE_EVENT,this.moveHandler.bind(this));
        Drag.dragElem(this.dragDiv,null,this.minDiv);
        this.minDiv.style.float=this.maxDiv.style.float="left";
        return div;
    }
    set width(value){
        this._width=value;
        this.render();
    }
    get width(){
        if(!this._width) this._width=0;
        return this._width;
    }
    set height(value){
        this._height=value;
        this.render();
    }
    get height(){
        if(!this._height) this._height=0;
        return this._height;
    }
    set imgSource(value){
        if(!Array.isArray(value))return;
        this._imgSource=value;
        LoadMethod.init(value);
    }
    set left(value){
        this.zoomView.style.left=value+"px";
    }
    set top(value){
        this.zoomView.style.top=value+"px";
    }
    loadFinishHandler(e){
        this.targetList=e.targetList;
       this.width=this.width || e.targetList["min"].width;
       this.height=this.height || e.targetList["min"].height;

    }
    moveHandler(e){
        if(!this.targetList || this.targetList.length<2) return;
        let widthScale=this.targetList["min"].width/this.targetList["max"].width;
        let heightScale=this.targetList["min"].height/this.targetList["max"].height;
        Object.assign(this.maxDiv.style,{
            backgroundPositionX:-e.point.x/widthScale+"px",
            backgroundPositionY:-e.point.y/widthScale+"px",
        });
    }
    render(){
        if(!this.targetList || this.targetList.length<2) return;
        Object.assign(this.minDiv.style,{
            width:this.width+"px",
            height:this.height+"px",

            border:"1px solid #000000",

            backgroundImage:`url(${this.targetList["min"].src})`,
            position:"relative"
        });
        Object.assign(this.maxDiv.style,{
            width:this.width+"px",
            height:this.height+"px",
            backgroundImage:`url(${this.targetList["max"].src})`,
            position:"relative"
        });
        let widthScale=this.targetList["min"].width/this.targetList["max"].width;
        let heightScale=this.targetList["min"].height/this.targetList["max"].height;
        Object.assign(this.dragDiv.style,{
            width:this.width*widthScale+"px",
            height:this.height*heightScale+"px",
            backgroundColor:"rgba(255,0,0,0.2)",
            position:"absolute"
        })

    }
}

html:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="js/LoadMethod.js"></script>
    <script src="js/ZoomClasses.js"></script>
</head>
<body>
    <script>
        let zoom=new ZoomClasses(document.body);
        zoom.imgSource=["img/max.jpg","img/min.jpg"];
</script>
</body>
</html>

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文章来源：https://mp.weixin.qq.com/s/bTObsRC7ElGfqSordDop7Q