16-1 ECMA5与ECMA6的函数定义

ECMA5:

function Drag(id){
    this.ele = document.getElementById(id);
    var that = this;
    this.ele.onmousedown = function(evt){
        that.fnDown(evt);
    }
    this.fnDown = function(evt){
        var e = evt || window.event;
        this.disX = e.offsetX;
        this.disY = e.offsetY;
        var that = this;
        document.onmousemove = function(evt){
            that.fnMove(evt);
        }
        document.onmouseup = this.fnUp;
    }
    this.fnMove = function(evt){
        var e = evt || window.event;
        this.ele.style.left = e.pageX - this.disX + 'px';
        this.ele.style.top = e.pageY - this.disY + 'px';
    }
    this.fnUp = function(){
        document.onmousemove = null;
    }
}



ECMA6:

class Drag{
    constructor(id){
        //属性
        this.ele = document.getElementById(id);
        var that = this;
        this.ele.onmousedown = function(evt){
            that.fnDown(evt);
        }
    }
    fnDown(evt){
        var e = evt || window.event;
        this.disX = e.offsetX;
        this.disY = e.offsetY;
        var that = this;
        document.onmousemove = function(evt){
            that.fnMove(evt);
        }
        document.onmouseup = this.fnUp;
    }
    fnMove(evt){
        var e = evt || window.event;
        this.ele.style.left = e.pageX - this.disX + 'px';
        this.ele.style.top = e.pageY - this.disY + 'px';
    }
    fnUp(){
        document.onmousemove = null;
    }
}