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;
	}
}