Lite Add button for Smooth Scroll to the top / bottom

为页面添加按钮，平滑的滚动到顶部/底部
当前为 2015-08-01 提交的版本，查看最新版本。
换行
// ==UserScript==
// @name	Lite Add button for Smooth Scroll to the top / bottom
// @author	burningall
// @description	为页面添加按钮，平滑的滚动到顶部/底部
// @version     2015.8.1
// @include		*
// @supportURL		http://www.burningall.com
// @contributionURL	[email protected]|alipay.com
// @namespace https://greasyforks.org/zh-CN/users/3400-axetroy
// ==/UserScript==
//=======快捷键======
//alt+1>>>>>>回到顶部
//alt+2>>>>>>去到底部
(function(document){
//================公共函数区============
function addEvent(obj, event, fn) {return obj.addEventListener ? obj.addEventListener(event, fn, false) : obj.attachEventListener("on" + event, fn);}
function getSize(obj) {return document.documentElement[obj]!==0 ? document.documentElement[obj]: document.body[obj];}
function scroll(obj,dir){//obj随意，dir>0往上滚，dir<0往下滚
	clearInterval(obj.timerScroll);
	obj.timerScroll=setInterval(function(){
		var position,speed;
		if(dir>0){//往上滚动
			speed = (getSize('scrollTop') / 10) + 1;
			position = getSize('scrollTop') - speed;
			if (position <= 0) {//如果滚到顶部
				document.body.scrollTop = document.documentElement.scrollTop = 0;
				clearInterval(obj.timerScroll);
				console.timeEnd('hello');
			}
		}else{//往下滚动
			speed = ((getSize('scrollHeight')-getSize('scrollTop')-getSize('clientHeight')) / 10) + 1;
			position = getSize('scrollTop') + speed;
			if (position + getSize('clientHeight') >= getSize('scrollHeight')) {//如果滚到底部
				document.body.scrollTop = document.documentElement.scrollTop = getSize('scrollHeight');
				clearInterval(obj.timerScroll);
			}
		}
		document.body.scrollTop = document.documentElement.scrollTop = position;		
	},20);
}
//================快捷键区============
addEvent(document,'keydown',function(e){
	e=e || window.top.event;
	if(e.altKey && e.keyCode == 49){//alt+1，向上滚动
		scroll(document,1);
	}else if(e.altKey && e.keyCode == 50) { //alt+2，向下滚动
		scroll(document,-1);
	}
});
})(document);