鼠标拖拽元素以及继承原生代码

实现页面上两个DOM元素的操作，通过继承的方式

class Drag{

constructor(ele){

this.ele = ele;

this.m = this.move.bind(this);

this.u = this.up.bind(this);

this.addEvent();

}

addEvent(){

this.ele.addEventListener("mousedown",this.down.bind(this))

}

down(eve){

var e = eve || window.event;

this.x = e.offsetX;

this.y = e.offsetY;

document.addEventListener("mousemove",this.m);

document.addEventListener("mouseup",this.u);

}

move(eve){

var e = eve || window.event;

this.ele.style.left = e.clientX - this.x + "px";

this.ele.style.top = e.clientY - this.y + "px";

}

up(){

document.removeEventListener("mousemove",this.m);

document.removeEventListener("mouseup",this.u);

}

}

class SmallDrag extends Drag{

constructor(ele){

super(ele)

}

move(eve){

var e = eve || window.event;

var l = e.clientX - this.x;

var t = e.clientY - this.y;

if(l < 0){

l = 0;

}

if(t < 0){

t = 0;

}

this.ele.style.left = l + "px";

this.ele.style.top = t + "px";

}

}

var obox1 = document.getElementById("box1")

var obox2 = document.getElementById("box2")

new Drag(obox1);

new SmallDrag(obox2);